BH vs Contractions

How do I tell the difference between them? And when should I go to hospital?

It all started last night when I was Black Friday shopping. I was walking around toys r us and all the sudden my stomach cramped up really bad. It happened a couple more times and then it eased off after I went to sleep. Well about 2am this morning I woke up to more cramps and a lot of pressure in my vagina. I woke about every hour after that with the same thing happening. I’ve tired timing them all day but there’s never anything constant. However, they do get really bad when I bend over. I just laid down trying to relax and they have started again but this time they are worse. I don’t know what is going on..😖