Braxton hicks?

Hey there! I'm 36 & 2 die may 19th. The last few weeks my belly has started to feel tight at times almost as if baby is stretching however it seems to be my whole belly not just one spot. Most of the time it's no big deal at all and other times it's just slightly uncomfortable. With my daughter I never had this....  is this Braxton hicks? Also when I do go in to labor will I be able to tell the difference right off the bat?