You say that being bi never bugged you. So--you've known you're bisexual, and that was okay? Because you were with a guy so you could "appear normal"? Or could pretend to yourself that you were?

If you knew you were bisexual, then you really were already to the point that you knew you aren't hetero. That's beside the point now. Now you need to come to terms with being bisexual or--as you now suspect--lesbian.

As a single mom, you've got a lot of responsibility. I hope you can get a therapist or counselor with some special understanding in this gender issue. You have a lot of work to do and need lots of support. Some of that you can probably find on PC.