Jessica Simpson is beggin' for help after suffering an extreme case of edema during her pregnancy ... one that's caused her left leg to take on more water than the Titanic.

The 38-year-old reached out to fans for tips on Thursday night -- saying, "Any remedies?! Help!!!!"

Edema is pretty common but if you're in pain, you should DEFINITELY go see a doctor.

Unclear when she's due, but Simpson announced her pregnancy back in September -- and with most people going public around 12 weeks, the assumption is she'll pop around April. This is her 3rd child -- she already has 2 with husband Eric Johnson, a former NFL player.

Tons of people have already reached out to Jessica with tips. Our advice? Condoms. But, we're not doctors.

At least J Simp's toenail polish is on fleek. Feel better!