Sorry, haven't read whole thread cos don't have the energy for the sleep training debate.
My first was like this. She slept all night with one wake up from 3 weeks. Nothing we did, total fluke. Then the 4 month sleep regression hit and it was hell! Total hell! Like you, every 45 mins to 2 hours. Every night. And DH was returbing our house so I was on my own.
I waited til 6 months on the nose and did controlled crying. It worked like a dream. 2 nights and we had a happier, more content baby and the difference in her development was staggering. Best thing we could have done for her and us.
As for naps, she was never a good napper until I tried 2 things:
Maximum awake times (literally the most game changing thing I learned as a new parent and has been others I've shared it with). Google it and you'll get the right awake times for your bubs, but basically I'd completely underestimated how much sleep a small baby needs.
Second was a dummy. I was always a bit anti dummy, had tried it in the early days when my nipples were bleeding but she had no interest. Tried it again one day when I was on an aeroplane and they wouldn't let me breastfeed (seatbelts on but held on runway for an hour) still not interested. Tried it one naptime a month later... again game changer. It was like a magic sleep button. I gave her the dummy and walked out the room and she went to sleep. We then weaned her off the dummy when we did sleep training later. But we were very strict wirh the dummy before that, she had it in bed as a sleep aide, never sny other time.
Neither of those things helped with the night time sleeping but at least stopped me rocking her for 45 mins for a 20 min nap in the day and gave me some quiet time.
Only thing I regret is taking away the dummy so early. A few months later she started sucking her fingers and she is now 3.5 and I have only just managed to stop that (with that yucky tasting nail polish... though once I tried that it worked overnight).
She is the best sleeper ever. 12 hours every night and regularly still has a 2-3 hour nap when not at nursery.
In the meantime, you have my absolute sympathy it is a hard hard time. I am currently 35 weeks pregnant wirh number 3 and this gives me the fear. Good luck with it.