6 weeks and feeling like 6 months

This is my 4th so I should be a pro by now but this pregnancy is throwing me for a loop. At 5 weeks I swelled up so much in the stomach that people didn't believe I was only 5 weeks. My boobs have already gone up a whole size and my stomach just seems to keep growing at a very fast rate. With my last one I didn't even show until 6 months but now I'm already feeling like I'm ready to pop. Heartburn all day, nausea all day, stomach is sore and sensitive. Anyone else have these issues/symptoms?