Burning pain

So ive been having sex with my boyfriend for a while and since im on the pills ive started to have burning pain ...

The worst is when we are done i cant even sit normaly because it hurt so bad ... i was wondering if it could be because of the pills or something else..

And it also hurt when he tries to come in me ... as if im to tight for it to get in without hurting ..

anyway have suggestion ...

i did learn somewhere that we create a liquide that reduce the acid in the sperm but what if i dont create enough and its the cause of my burning pain....?

Im really comfuse right now and i dont know what to do