3rd trimester morning sickness??!

I am 34 weeks and ended up going to the hospital this last Saturday for contraction pains. It scared the crap out of me, since during my first pregnancy I barely even had any BH. It took a while to get the contractions to stop because I couldnt keep anything down including water, which scared me even more. Eventually they did stop and we found out I had a UTI which I was given a prescription for, but I was told the nausea was just 3rd trimester morning sickness... since then I've barely been able to keep anything down and I've been very lethargic. I was just wondering if I should be worried/call my OB or if I just need to tough it out