any suggestions?

So I am 35 weeks and 2 days and I am extremely constipated to the point I can barely get comfortable. I have a underactive thyroid so was constipated before but now I can't even go at all or if I do it's a few little pellet type poops.. I have taken milk of magnesia the past 2 days and of course I'll get a few little pellets out but that isn't helping. I'm not sure if baby is blocking the rest from coming out or what but I just have so much pressure down there and when I try and push I get nothing. I don't know what else to try.