Low level depression

I think I have a fairly constant low-level depression - not feeling sad, but just the constant lack of energy. Like, I work a full-time job and 2 part-time jobs right now, and when I get home, I just sit on the couch and don't have energy to do anything. Once little one is here I plan to go down to just my full time after my 3-ish months of maternity leave are done. I just worry that I won't have energy to do any parenting at all if I am depressed. Has anyone felt like this and felt better once they had their baby?