It sounds like your life can be very stressful. That is often the case in your situation. However I would encourage you to consider that he was an equal participant in this affair although he may be genuinely sorry for his behavior. Couples do recover from stressful parenting problems and even an affair. The reasons that you might consider relationship work could address many issues. When you have support and counseling you can begin to lessen stress and deal with the issues post affair. This will be even more important when the baby comes.
When you doubt your partner's word even legitimately doubt this there has to be work to restore the trust that exhibited before. You may find that to be marital counseling or self help but it is necessary. You can even access marriage counseling online or by web cam by Googling online therapy. The real issue is not the modality but instead identifying why you doubt his word and what it will take to restore trust. The may mean that he has to be totally accountable for his actions to take the focus off of her who isn't your responsibility. I encourage you to look for a professional and approach this by addressing the need for the other relationship and develop ways to relieve stressors.
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