It's really hard when they're that young. I think a lot of separated families don't start out with 50-50 visitation with infants, especially when they're still breastfeeding.
Is it looking like it might be a relatively harmonious divorce? Would you STBX be willing to do a slow step-up to visitation? You might propose a schedule where he takes the baby for several hours two or three times a week, progressing to full days or overnights a year or two down the road. Have you been able to have any logistical-type discussions of what kind of visitation he'd want?
As far as being away from your child goes...I my case, now that DS is almost three and a half, I actually really appreciate that he can spend time with his dad, stepmom (a really lovely, sweet and nurturing lady who parents her kids in an AP style very similar to mine, I feel totally comfortable knowing that she's watching DS) and stepbrothers and sisters. He gets to build a good relationship with his dad and stepfamily, and honestly, I appreciate the break. My life is really busy with work and school, and it's nice to have a solid block of time to clean the house, catch up on homework or hang out with my friends and boyfriend. I do miss DS, especially when he's gone for two nights in a row. But I definitely find that I'm a better and more engaged mother to DS when I get some adult time. He hasn't had an overnight in the last three weeks because of his dad's wedding, then my parents coming for a visit, then his dad going out of town, and honestly, I'm sort of looking forward to having next weekend free.
I won't lie, being a single parent can be hard, and dealing with custody issues can be hard. But if you have the luxury of being in a situation where all the adults are acting like adults and thinking with the child's best interests in mind, then it really can work out for the best.
Are you in a position where you'll be able to live off of child support and a few hours of work per week, or will you have to jump back into the labor force full time?