Contractions or gas?

Im 36 weeks pregnant and I’ve been feeling pretty weird these past couple days . My legs are extremely sore to the point I can’t even walk feels like I worked out . Also my breast are very sore as well they’re so sensitive I can’t even touch them . Also I’m experiencing period like cramps and I feel constipated and like I have a lot of gas or trapped gas it’s hard to explain I really don’t know what to do or what it might mean . This is my 3rd baby