Feeling pressure during SEX!?

Hey so when I decide to have sex and A guy sticks it in and starts getting a rhythm, I get this uncomfortable pressure. Like if my pelvis is going out and in ( that’s probably so dramatic lol) Or you know if you go to the doc and they stick that long thing in you and push on your walls and there’s pressure, it kinda hurts? That! It’s just uncomfortable and painful and makes me feel like there’s something wrong with me. Like I can’t take the “D” Currently I’m not in a relationship and don’t have sex often but does anyone else have this problem? Do I just need a small guy or will my vag get used to it and sort of expand and it’ll feel better. Btw sex can be okay sometimes I just have to push the person out a bit. Idk. I would just like to enjoy sex a bit more!! I do have a toy and that’s all good but it’s mainly to touch my g spot. Just putting that out there in case it matters haha Any tips?