Greenish discharge 34 weeks pregnant

Hi there, Please help as this is quite urgent and I dont know what this is. I am currently 34 weeks pregnant and because this is my second pregnancy I know that discharge in pregnancy is normal. Ive had alot of discharge during this pregnancy however this morning I had a bit of a shock. I went to the bathroom and saw I had alot and I mean alot of discharge which is greenish in colour and smelled really weird with clots in. I had really bad stomach pain and heartburn in the past couple of days and my docter gave me some gaviscon and Maxolon T. Is this discharge due to the medication or maybe preterm labour? Please help I dont know if this needs more attention...