Do uti's feel worse before they get better?

Nicole
I'm 34 and have never really had one before- I think I did 7 months ago but suffered through it naturally and it went away in about two weeks. 
This time I am 24 weeks pregnant and taking antibiotics. My issue is that after I take a dose, I have the urge to pee much more and the tingling/burning in my bladder gets more intense. Is it from the medicine doing it's thing? 
I didn't take one yesterday because it's so intense. But this morning I did and I have to stay close to my bathroom...just hope it's a flushing out type process?