are you bipolar 1 or 2 ? do you take any medication to stabilise any excesses in mood or behavior - and/or do you see a therapist ? are you always depressed or is it because you're on a "down" ? why does your parner suffer from ptsd ? has this anything to do with the fact he needs to "look good" (knowing people - having friends) ? is this why he lies basically ? is ge overcompensating with his child because he feels he's no good - in which case - has this anything to do with the mother of his child ? what relation are/were they having ? is she putting a lot of pressure on him to "perform" with the child and be "a good father" ? (which of course will only accentuate any ptsd) - apparently he does a number of things to "suit" him because he's in need of validation and encouragement : then of course you being upset because of him and the way he treats his child - is not going to arrange things necessarily - for him - for the child - for you - why are you no longer interested in sex : is it in sex - or sex with him ?
often these ways of going about things / handling situations in a relationship go in cycles that become habitual when repeated often - then ingrained and repeat themselves automatically and then the relation of course can not really get better but only worse : at one point one has to exit the vicious cycle somehow - take a break - get away for a few days or what : something to break the addiction to repeating behaviors - oneself and together - you both might need to get some perspective and understand where you're each coming from and how that plays out in the relation - then come up with things to do to change behaviors, attitudes and ways of communicating - nobody can find a solution when stressed out and in depression
start with considering concrete happenings in the moment - not things said or done yesterday : deal with situations in the now - so as to be able to bring forth objectivity on actual facts and then take it from there with concrete possible solutions - one step at the time - one day after the other
sometimes things get in a knot : then one has to undo the knots one by one - and that may take some time