I was admitted at 27 weeks with the same sort of thing. Contractions were 1-2 min apart, but not in PTL either. Mine was related to a degenerating fibroid, dehydration, and extreme constipation (take your pick).
Sorry there's no clear answer for why this is happening. I agree with PP, you need to take it easy. My contractions also came on after working a string of 12 hour night shifts. I went to turn a patient and he went into a lethal dysrhythmia. They started then. 3 days later I was admitted.
Remember, you're getting closer every day, and stay focused on the mile stones. I've celebrated each week I'm closer to term. I never thought I would get here with all of my risks. Hang in there and let us know how it goes.