I can’t relate completely to how you are feeling but hope I can be of some help to you :)
I’m a first time mum and felt so overwhelmed when I found out I was pregnant (even though I wanted to be pregnant). I couldn’t even talk to my partner about it, every time he mentioned it I just closed up.
I was honest with my midwife about how I was feeling and she was very supportive and has offered me help in the form of mental health support - although unfortunately I’m still waiting for this.
However, one evening I just opened up to my partner about how I was feeling, I told him everything and it was the best thing I did. He reassured me more than anyone else had been able to. He made me feel as though my concerns were completely acceptable and we talked it through.
I would also say (as I’m sure you know from your first pregnancy) that hormones were definitely a huge thing for me, most days for me (up to 12 weeks) were terrible, I just wanted to cry and hide away and pretend it wasn’t happening but I can say that in the last week - 2 weeks I’ve felt 100 times better. I do still have bad day’s but more days where I feel able to cope with it.
I know our situations are slightly different but just wanted to throw it out there.
I have also had a termination previously so know this is a really difficult thing to do but if you are really sure it’s what you want you will be supported. I never really got counselling after and so If you do go down that route one thing I would say is Make sure you get support from the clinic and you allow yourself time to recover - no matter what people say/think it’s still a difficult decision to make.