Regretting marriage and pregnancy

I’m 28 and husband is 43. 6 months pregnant. We got married in September. We started “trying” in December and got pregnant in January but I didn’t listen to myself about maybe not wanting kids, because he’s older and I didn’t want to wait longer for that reason.

He’s a great person and very supportive. But I just don’t feel a connection with him anymore. Only had sex twice in the past 6 months—not even on our (delayed) honeymoon. And I don’t feel like I want this baby. I keep fantasizing about leaving after birth and going on a solo trip and leaving him too. I feel like a horrible person but I have mental illnesses and I’m afraid I’ll be a bad mother because of it and he and the baby would be better without me—meds and therapy don’t do the trick but I’m still sticking with them. Advice?