Sacha - I think that the ebb & flow makes us feel like we have it under control. However, if you feel it is making things harder than they already are with (life with an infant - - especially one with reflux/colic, as I know, too - - is NOT EASY), then please seek out help. You do not have to suffer through this. It isn't a matter of pulling yourself up by your bootstraps or "snapping out of it" as some people will make you think. This is a hormonal imbalance that affects how our brain is sending & receiving signals.
You are not weak, you are not a bad mom/wife/person, you are not self-absorbed (I think I hard all of those things from myself or from others), you are dealing with a REAL illness.
I don't know your situation, so perhaps I'm over-reacting. I just know how difficult the PPD was for me & I'm still dealing with the ramifications now. It actually spurned on a major depression for me later, which I'm working to come out of. I thought I was losing my mind - I actually believed I was having a nervous breakdown (and who knows, maybe I was). I should have sought out help earlier.

Sending you hugs & encouragement. I'm sorry that those early months were so difficult for you & your baby. Being a mom is hard - it leaves you so emotionally raw in ways that no one can prepare you for. But those tender moments that come around every so often will remind you that it is 1000x over worth it!