Its been almost a year since i had sex &i dont mastrubate,now i had protected sex but i am feeling pain in uterus and lower belly, i also felt my vagina smaller while sex during the behind position. is that normal?

After prolonged sexual abstinence the vagina becomes tighter and makes penetration uncomfortable for the first few sessions. I'm not sure that the uterus is affected. Abdominal muscles can be somewhat strained during intercourse.. Use adequate foreplay,lubrication and gentle techniques.and I'm sure sexual activity will be pleasurable again.

Size of the vagina does not change. In some positions it seems so. Your discomfort might be related to not having sex for a year. If it persists pl see a Gyn.