The next time you feel that pain/feeling feel to see if its somewhat swollen in that area. It could be vericose veins it causes you to feel pressure down there and it's common in pregnancy.
I get those and they are normal its mostly your pubic bones softening up cause one time mines were so bad that i seriously thought the baby would come out but all my midwife said you'll be fine...i am fine but those pains are gets pretty bad at least for me and im only 35weeks.
I usually have pains like that the day before I have my period. But just to be safe I think you should go to the doctor if the pain gets worse.