Thanks for writing to Just Answer.
I'm afraid you may be rushing things by asking for a committment of fidelity from her while you are not yet available (divorce still in progress.)
Once the divorce is final, are you planning to marry this woman if the relationship progresses? She is quite a bit younger, never married. Does she eventually want children? Do you want more?
Not many 33 year old women will commit to a long-distance romance with a man who has his kids every other weekend--unless there is a long-term committment (read: marriage) in sight.
What is she supposed to do while you're with the kids on the weekends? Are you willing to incorporate her into their lives? Does she want to be involved with your children?
She not want a boyfriend, or she may want a boyfriend at the same stage of life as she is...just starting out. At 33, having a boyfriend does not usually involve responsibilities. I think you may open a can of worms that you will wish you hadn't if you ask her not to see anyone else.
Enjoy the time with her that you have...bringing things to a head may well bring them to a close.
Sorry not to have a more encouraging answer for you, but I feel that people who write to us deserve honesty.
Please click on accept if this has helped clarify your situation.