So kinda freaking out! Never noticed this??

Okay so I had a baby about 5 months ago! And currently working on #2 it took me awhile with my first baby about 6-8 months but everything has been fine during sex no pain or anything well tonight my uterus felt really low. Like when my fiancé would put it in it would kinda hurt if he went to far... well TMI! But I was feeling around in there and I guess it’s my Cervix but it’s a huge hole! Like probably about half the size of a dime maybe? It’s open though. Feels like it’s a whole. Idk really creeped me out bc I’ve never noticed that! Ever! Is it bc I just had a baby? Really fertile? Something probably wrong? Help! Tia!!