If you are having doubts of this level, then you should stop trying for a baby - NOW.
You need to think through how you feel about what has happened, and whether you really can move on from this to a future together based on trust,
The fact that your partner is refusing to face up to his affair, and deal with it in a mature way rings loud long alarm bells.
It means he is immature, and unwilling to deal with issues - which does not bode well for raising children. It also raises serious questions about his willingness to address his actions in terms of their short and long-term effect on you, and your relationship with him.
You need to be far more sure of him and your future together before you even think of bringing a baby into the equation.
For a couple in a stable relationship with a deep bond and mutual respect and trust, a baby is just bloody hard work!
For a couple without these fundamental basics in their reletionship, a baby spells disaster - for you, wo may well be left to care for your child without your partner.
Suggest counselling for both of you - and if her refuses, you should seriously start thinking about whether you really have a future with this man, and from here, the signs do not look promising.
Take things a day at a time. Talk it through with professional help, and then decide if you want to try and rebuild your relationship.
When - and indeed if - you get to that stage, you can think about having a child together. if you are imagining that a baby will 'bond' you together, be assured it will have the opposite effect, and non-one least of all a baby, dserves that start in life.
You have some thinking, and talking to do - that is your priority, and sex without contraception is simply not an option.
Good luck.