Yes the situation does all around suck. Hard to think it will never really go away. Chances after the 18 years of CS the child is coming looking for dad and time to get ready for something new. Even if I decided to end my marriage and move on CS will still be paid leaving less for COM and one day I'd have to deal with OC and COM as adults. No end.
Why do you regret telling your mom?
Yes, my H tells me the same thing about not being embarrassed. It is him and the OW that look bad. That doesn't help me much. I still feel people will think I'm stupid for staying or pity me or relish the fact of whatever isn't good in their marriage-mine is worse.
Looking back I wish things had gone differently. When my H found out OW was pregnant and it might be his or someone elses him and I were at a turning point in our relationship. He had already ended his affair with her (she waited 5 months before telling him she was pregnant) and him and I were picking up the pieces of our broken relationship and moving on. He knew after hearing this from her that I would leave so he confided in his mom who told him not to say anything to me until he knew for sure he was the father cause there was no point in getting all worked up if he wasn't. Even when she contacted him after the birth to say the other man tested came back 0% his mother told him to wait and tell me, but he told me right away (I should have known my MIL was a [censored] even back then...but she's 2 faced)
I wish my husband had come right to me and we could have kept everything just between us and not told anyone at all. The reason other people found out was because of my MIL & FIL befriending OW on facebook and commenting on her pictures. I regret telling my mom because of course she looks at me bad for staying in the marriage. I'm even nervous to tell her I'm pregnant now because I know she'll say something about my husband having another kid.
I know how hard it is to not be embarrassed. I often wonder if we feel this weight of the embarrassment, how OW's even live with themselves with the embarrassment they must feel of walking around with a child that screams you're a home wrecker. But then I realize if they were smart enough to think that way...they wouldn't be OW's in the first place let alone OW's who are stupid enough to get pregnant and keep a married mans baby.
I feel the same way about even if you end the marriage. It's not like it even goes away then. You're still left with the resentment because now you're getting even less than the OW since she tied up the finical resources first (even if you had the kids first). Not to mention the "defeat" of the OW getting exactly what she wanted by breaking up a family.
I wish there was a better solution. All I can say for now is to focus on your marriage. Focus on making you guys strong again...it took us a little while to get there and the thought of this situation never leaves your head. But as time goes on if you build your marriage stronger you will be able to face it all together and you will take joy in the victories you get by keeping your marriage together.