Need help with my son 😭 not coping

My son is 18 months next week and he is so different to my 3 year old.

Every child is different but with my first daughter I never had it this difficult it's actually really sad it's come to this ☹️

1) my boy is waking up the last 2 weeks all night not sleeping !! He starts screaming!

2) his gums are bleeding when I'm brushing his teeth and his teeth look TINY because his gums are so swollen. Should I check up with the dentist? Or this normal for teething??

3) definitely separation anxiety anytime we leave the room he absolutely screams his head off.

4) he's very clingy all of a sudden and he's constantly wanting to be picked up and cuddles.

5) he's out of character a lot and it breaks my heart he looks all sad and bored of life :(

The biggest issue for me is the separation anxiety, I hope this gets better as I'm due my third baby in three weeks.

(I got pregnant regardless of the implant in my arm so before people come at me for having another baby yes I did prevent it with contraception that's worked well for years before any kids it's a massive shock) plus I been with my bf for 6 years the implant worked for us before!!

I don't know what to do I can't handle this being tired and him being tired also. He is so different these days and I think he knows I'm having a baby even tho he isn't very vocal with words etc!

Really shitting myself for when baby comes that he will still want to be picked up all the time etc

What could this all be? Does it get better?

I'm calling health visitor Monday and getting advice but any advice now would be appreciated x