I don't know if I can be much help.

Maybe you need to do a pros and cons list for the 2 jobs. If the second job isn't going to be anymore stimulating the only plus for that really is the extra money, but then you said you will be paying more tax.

On the otherhand, if you increased your hours at your current job, as you said you are TTC, you will qualify for Maternity Leave and get it at the higher rate, so does that outweigh the benefits of taking the 2 days a week with your old employer.

Hard decisions for you.