why cant parents respect boundries??

when i was younger i was very touchy but as ive grown up ive become a little more iffy. for the past few years i was "only my friends can touch me, not my family" and recently its become "no one can touch me". the reason that changed completely is a long story but ill try to shorten it as much as i can. 

basically, over the past couple of months my dad has been finding it "funny" to poke my arms and literally touch my butt??? like um okay bud maybe lets not touch ur 15 yo daughters ass, huh? anyways, when he'd do this stuff i'd physically back away and make uncomfortable noises. enough to let a 54 yo man know that im uncomfortable with what he's doing, right? not to my dad apparently. so about a month ago now, on my older sisters birthday, we went to a pizza place for dinner with our cousins and mine and my older sisters friend. after parking and walking up to the place, my dad tried to slap my ass but thankfully my phone in my back pocket stopped his hand from actually touching me. i whispered to my friend "dude my dad just tried to touch my butt" but i dont think she rlly heard me cuz she didnt have much of a reaction and trust me if she heard me clearly she wouldve made something like this a big deal. so anyways, after we finished at the pizza place my family wanted to take pictures cuz it was my sisters bday. i was standing next to my friend when my dad started poking my arm and i told him "stop or ill kick you" and u know what his fucking response was? to his 15 yo daughter? "then ill break your legs". what the actual fuck dude. my friend kinda looked around and she looked uncomfortable. i started backing away very slightly. and yknow what he does next? he fucking ATTACKS ME. PINNING ME TO THE GROUND ATTACKING ME. IN FRONT OUR FAMILY. IN FRONT OF MY FRIEND. but yeah uh i eventually like crawled away and i started crying cuz what the fuck was that for. later that night when i got home i just stared at myself in the mirror and cried. my mom then texted me to come do the dishes but no way was i going downstairs especially while crying so me and my mom didnt exactly get into an argument but we were going back and forth abt the situation over text. she was siding with my dad and saying this happened bc of my "lack of communication". i made is physically known i didnt wanna be touched. it was his fucking fault as a 54 yo man who didnt read physical cues. but yeah i told her how i felt abt physical touch and she just kinda brushed it off.

i mention that story bc thats why i dont like physical touch anymore. 

ive found myself more aware of what i touch now. my shoulder will brush up against something and the feeling with stay there for another 20 minutes. when i touch something with my hand i have to IMMEDIATELY wash my hand or ill go crazy. the feeling stays there if i dont wash my hand. i never used to get these things before. like i could touch something and never think of it again. but as i mentioned, thats not the case anymore. 

so the entire reason im posting this is bc my mom cant take a fucking hint and accept that i dont want to be touched. im honestly scared to tell this next part cuz im scared ill seem extremely selfish but whatever. 

my little sister was diagnosed with type 1 diabetes last june and she likes to have ppl hold her hand when taking insulin bc its in a needle. she got a port or whatever so now she doesnt need to do pokes everytime she eats or needs a correction so she just puts the insulin in the port but yknow ports need to be changed out every few days and her sensor needs to be changed out every few weeks, so she still sometimes needs people to hold her hand. now i have a mom, older sister, and dad who can perfectly hold her hand for this stuff. she also has done pokes while holding a stuffed animal instead of a human hand before and she was just fine. but for some reason, whenever doing something that involves a needle, im her go-to. i get that im her sister and need to be there for her but i rlly cant to physical touch anymore. my mom knows that. but she still pushes me to hold my sisters hand. my mom did this the other night and i didnt realize how bad my resistance of having physical touch was until then. my little sister gets like nervous when doing this cuz its a needle so she'll like take a while to actually do it sometimes. the other night, she kept holding my hand then letting go and eventually going on whole ass side quests before actually putting her new sensor on. everytime she let go of my hand i felt the need to wash it. but i couldnt, cuz if i left, my little sister wouldve gotten upset. even if i just left to wash my hands and come back. so everytime she let go of my hand i just hand to stand there while i still felt her hand in mine after she let go. and everytime she'd hold my hand i'd tense up cuz yknow i dont wanna be touched so im uncomfortable. my mom kept giving me dirty looks and said to just hold her hand. but the way i see it, why make me uncomfortable just for my sister to be comfortable? thats not how things should work. both people should be comfortable. 

but yeah, after that, i went into my room and just kinda cried. not heavily, but i cried. my mom walked in as i was blowing my nose and just quickly stopped crying and told her that all i was doing was blowing my nose.

so my question is, why cant parents or at least mine just accept that i dont want to be touched. its not that hard to accept. just bc im ur daughter and my sisters' sister does not mean i am required to give any sort of physical affection.

writing this was very emtional. i had to pause multiple times and take a break so i wouldnt cry. its rlly a subject that i wish my parents understood better.