It sounds like hemorrhoids to me.

Hemorrhoids are painful, swollen veins in the lower portion of the rectum or anus.

Causes, incidence, and risk factors
This condition is very common, especially during pregnancy and after childbirth. Hemorrhoids result from increased pressure in the veins of the anus. The pressure causes the veins to bulge and expand, making them painful, particularly when you are sitting.

Don't be embarrassed it is a fairly common pregnancy thing. Have a chat to your GP about it (or other health care provider) and they will be able to recommend a safe hemerrhoid cream for pregnancy. Your pharmacist may also be able to help if you want something tomorrow.

There are other things you can do to help hemorrhoids too - don't strain to poo so having plenty of water and fibre will help with that. Pregnancy causes constipation often which in turn causes hemorrhoids.

Lots and lots of pregnant women get them. It's best to get them seen to because they can just get larger and more painful if you leave them.