Can't sleep!

I just hit 31 weeks today and for the past wk I've had a terrible time sleeping at night. This is my 3rd pregnancy so I completely understand that I will have trouble sleeping but I can't figure out what's going on. Normally, I'm kept up by limbs going numb, having to pee, or just having some discomfort somewhere. BUT for the past wk I just can't pin point the cause to try to fix it. I have a 1 yr old and 3 yr old that I stay home with all day so I am 100% exhausted come bed time. I just can't seem to sleep. Anyone have any tips or tricks that help them sleep at night??