I am normally a confident, balanced, logical person, if anything less anxious than I probably should be at times.
I do really badly with hormones though and had a huge sense of doom during pregnancy for no reason. I didn't even really dare talk about it. I was sure I would lose the baby or they would be seriously injured or have significant disabilities, wasn't sure I'd make it either. The baby was born fine, I'm also fine. So please know that this doom feeling can arise from hormones etc without having any validity and has nothing to do with what will actually happen in your future.
For me the thoughts continued to some extent after birth and during extended breastfeeding. I was sure my baby would die before the age of two and would avoid discussing anything after this age. That baby is 2.5 now, healthy and happy and particularly since stopping breastfeeding my doom feeling has tailed off and I can now think about the longer term ok.
From my experience I wouldn't necessarily expect CBT etc to help (not that I tried it) just because CBT as I understand it is about rationalising, and this doom feeling is absolutely irrational but feels very convincing. I'd look more to things that might make you feel better in each moment while you get through this period of time - e.g spending as much time as possible being around good people, in nature or with pets/animals, doing yoga/meditation/relaxation/walking etc, things that feel comforting to you (dressing gown, fluffy socks, soft toys, snuggling in blankets, hugs), anything that lifts your mood maybe citrus shower gel, sniff or diffuse essential oils you like, watching funny or uplifting tv/films/books, foods that appeal, buy yourself a little present here and there if you can. Literally just being kind to yourself and treating yourself gently, because you are having an unpleasant time living with this feeling just now and you deserve to be looked after, supported and pampered while you get through that.
I still remember after childbirth the enormous and overwhelming feeling of relief at just not being pregnant any more, pregnancy was such a horrible state for me it was just wonderful that it was over, even before it had sunk in that my baby was ok. Maybe that feeling is something worth trying to visualise. You will get there! All best wishes for you and your baby.