Well, not necessarily a bad parent, but a less good one anyway.
Ex had an affair with a mutual friend for 2.5 years, sleeping with her repeatedly in our bed while I was at work (he was sahd). There were times our younger child was shut behind a stair-gate while they were in bed (2 at the time) and it is possible that a child was conceived, though the woman claims a dna test proves otherwise. H happily waved me off on playdates with this woman so she could lie to my face as well as him. He knew for a year her h knew and was threatening to tell me yet he carried on the affair. Her daughter was friends with ds but seemed to delight in winding him up. We discussed several times limiting the time they spent together but h continued to go to the park every fucking day after school - I know now so he could spend time with her mother, so put his 'relationship' above the welfare of our ds.
Yet now he is super-dad. Has moved out but sees dc every day except Saturdays, at the family home as he provides before and after school childcare and he lives somewhere unsuitable to take the dc, though does take them to gps fairly regularly. Obviously the dc know nothing about the affair.
The elder ds is now very sporty so loads of shared interests with his dad. Dad taking him off to late night matches, against my wishes, particularly as ds is tantrum-prone atm (he's 8 
). I am feeling pushed out. Today ds was disappointed not to be seeing his dad. I try to take an interest in his sporty stuff but it's all new to me and I feel like a poor-quality second choice. Although I 'have' the dc as h told me he would never take them from me, he probably spends more waking hours with them than I do still, due to my job. As well as that, I have to fit in housework, chores etc, which h doesn't as they are never with him in his space only mine, which he still gets to enjoy for free. Yet I have to feel grateful as he is here at 6.30 every day. I have looked into other childcare options but there is nothing affordable that would allow me the flexibility I need.
I feel like I am losing my dc, especially ds1, and I don't even know how to spend time with him in an enjoyable way anymore. We were always so close, despite working f/t I prioritised them every moment I wasn't and h even told me he didn't feel like the primary carer when we split, despite his having been a sahd since the beginning. I feel so resentful that they don't and will never know what their dad did, yet I would never want to tell them as the only motivation would be spite and it would be disgusting of me, yet I can't stand that he has walked away from this smelling of roses. All I can visualise is a couple of years time ds1 going to live with his dad, or blaming me that he can't because he will see it as my fault h has no money for suitable housing.
Can't see a way out. We have been split a year and I am over him, but can now see ongoing problems and issues that will never go away. A pointless rant at the end of a very depressing Saturday. The awful thing is I think I actually prefer being at work to being at home. Seems all I do is struggle against the dc to do things they don't want to do, but if I don't I feel shit that they have done nothing worthwhile.
AIBU?
To think that infidelity makes you a bad parent but that I will lose my children anyway
thinkingmakesitso · 13/06/2015 18:54
Don't beat yourself up
It sounds like you're doing a great job
Don't worry about being sporty with your ds, leave that to Dad
But re establish your bond with ds, take him for pizza maybe? Play cards tonight, teach him how to play rummy or uno?
And try not to think about the future, it'll all pan out 
I remember your threads. He always was an incredible cunt- but you always tried to defend him...you did well to get rid of him.
Your kids love you, they do. They love him too- which is annoying- but you are the mum. Try and spend some time with ds1- they often separate from their parents a bit - as long as you are loving and open - and you always have been - they'll come back.
Wishing you well. He put you through a horrible time.
To comment on this thread you need to create a Mumsnet account.