Sounds quite familiar to us.
Our first was awful from about two weeks to 5months (when we gave him mushed up solids) as soon as we got him onto solids he was like a different child. Don't get me wrong he was still a baby and then a toddler. So getting up a couple of times a night to resettle was expected. Now he's 4 he still walks and likes a cuddle, but now he comes to us, then goes back :-)
But the scars of going to work on 1 hour sleep and the feeling of dispair run deep. We sort of fell into the habit of me doing the nights and my partner had him all day (that was she got some restbite and sleep). We then did alternate nights.
I was also more able to put him down in the living room and walk away for five mins and let him scream as suggested by the midwife's. If he's screaming he's breathing.
It put me off having number 2. But we did, she was colicky too, but differently she's been a general whinger and whiner. But again the first 12-16 weeks were horrible. But the big difference was I knew there was an end to it. Well certainly every night of screaming. Number 2 is very different, still demanding but different.
As a mum you are all over the place in the first 18months, you're hormonally prone to feeling down and have feelings of despair. Never be to proud or "to tough" to speak to your doc, midwife or health visitor about your thoughts. My partner was fortunate to be able to get access to Councillors via works wellbeing program as she refused to accept she and any degree of PND. Looking back now 3-4 years she'll just about admit to it.
Having number 2 and going through year 0 scared me. It made me miserable the first time around, the second time the I my thing that kept me a bit more with it was knowing the end was coming. With my two food was the key to getting colic in its box.
PTSD... Absolutely possible, it's not a daft idea.
P.s. I type this with number 1 asleep next to me and number 2 sat on my lap sticking up mucus into a towel (bronchiolitis). 2 woke 1 coughing.
So much for my early night, mummy is at work and I'm on early morning duty.... Booooo.