Help!

I'm 33 weeks and 4 days and last week I had some light sporting but it was only once and I ignored it as nothing but now I'm starting to think it was the bloody show, I've also had a terrible flu which I'm still struggling to get over and it just seems to be getting worse for about 5 days now! This morning I started cramping but it doesn't feel like Braxton hicks, it's more like menstrual cramps and they have been constant since about 9.00am and don't seem to be calming down, they've started to become more painful now and very uncomfortable and I feel like I just need to go to the toilet. I'm worried that maybe being sick so far along is causing pre term labour? How will I know if I need to go to the Drs or if it's nothing? I'm a big worrier and can't do the waiting game because of my stress levels.