So it sounds like you enjoy being with her. There is a physical need there for you. I can totally understand that. I've walked in your shoes!

The issue I ran into is that feelings will start to manifest. What if you want more from her? What if you wanto be with her in a full relationship?
Then serious decisions will need to be made. For both of you.
Is she willing to walk away from a marriage?
Are you willing to accept her if she is? Do you really know ea other outside of the bedroom?

It's a huge step.

Only going from what you wrote it sounds like she is in this marriage bec of her child. It doesn't sound like she wants to give that up.
So would she be willing to leave her marriage & take the child with her? Can she financially do that? What about her husband?

Many many issues surround the outcome of this relationship. Right now it sounds very physical. So you both might think "why should I give that up?"
But are you able to compartmentalize your feelings knowing that she will always afterwards turn back to her family.
Do you have serious feelings for her?

This is where lines get drawn. Some people get into quick affairs bec of physical reasons. A need or want.
But if you've been having an affair for awhile it's hard not to develop feelings.

I'm glad you're looking down the road as to what might eventually happen. Most don't when it comes to affairs. Serious damage to many can be the result.

I think you really need to talk to her & ask her where this is going. If she says she doesn't know I'd table the question & wait til you got an answer.
Bec there will be heartache. I guarantee it.
Just my opinion, but I totally know your situation.