That sounds exactly like what i experienced the other night Summer (i'm 31 weeks) - i ended up with really bad gastro, when the gastro stopped so did the pains, it really freaked me out though, I was terrified i was going into early labour.
Thats what i thought as well. But its been 2 days now and i threw up only once which i think was more because i had severe heartburn and needed to relieve it. The pain is still persistant, if its still there by monday i might see my GP.