How to keep the flame burning with newborns?

Looking for advice...my husband & I have a 4 month old, and an 18 month old. So we've been through 2 pregnancies and 2 newborns in 2 years. We're stressed to say the least. Lately it just seems like we're co-workers trying to make this family run smoothly instead of actually being in love and enjoying each other's company. We're constantly bickering over stupid little things and it's taking a toll of both of us. Does anyone have any good suggestions? Even when someone offers to watch the kids so we can "go on a date" or something, we just use that time to SLEEP. We both work 40+ hours a week and I just don't think I can handle much more of the fighting.