While I can understand where you are coming from Fabby, I think we need a bit more info from the OP.
I felt very similar at several points in my relationship, and I would say that early on in my children's lives were particularly crux times.
I could tell you that we rode them out - and that now our dc are 7 and 5 things are much better. but it would be a lie there can be ebb and flo in any relationship, it's why you promise for better or worse when you get married - IMO.