Pregnant, Lower Back Pain, Abdominal And Groin Pain, Nausea, Excess Discharge. Painkillers Taken. Suggestions?

hello,
im 33 weeks pregnant with my 2nd child. since last night ive been having really bad lower back pain, a throbbing pain which was coming around to my sides of my belly and my belly has been tightening aswell. I took painkillers did a hot water bottle and went to bed, took me ages to get comfortable but i eventually got to sleep. woke up this morning and still had a back ache but not as bad, since doing some house work and walking around the supermarket i now have pain in my lower stomache and groin. I feel nauseous. and when i got out of the car i had a wet patch on my trousers, i did not need too wee though :S ive been having alot of discharge since yesterday too. do you think im in labour as im starting to get a bit worried :S thnaks