Should I be concerned?

I went into pre term labor at 30 weeks and again at 31 weeks my doctor put me on terbutaline pills 3 times a day to keep from having contractions. I will be 35 weeks tomorrow and I have been loosing decent sized hunks of mucus plug last night and this morning. I do still have contractions on the meds but they are weaker and not regular. Last night I was having some stronger ones getting closer together so I took another dose of meds and they stopped but should I be concerned I have been loosing my plug??? This is my second kid and with my first I remember loosing a little of it a few days before delivery.