What shall I do about this affair?

I met a woman through work last year and it was definitely obvious we both found each other attractive. However I had a girlfriend and didn't know her situation. I then broke up with my girlfriend in march. This girl who I knew from you work contacted me & told me she liked me and wanted to take the opportunity in case I become unavailable again. So began talking over the phone for a few weeks and it was positive and quite a lot of flirting. Then she tells me she has a boyfriend and has been with him 10yrs.

I told her I wasn't interested in an affair and that we can be friends but would be open if her situation changed. She accepted this and we kept things just friendly. I then went away on holiday. The morning of she asked if she could see me before I went... We met up and before I left she kissed me and I kissed her back, our chat whilst away was more flirtatious. We returned and she became much more foreward with me and we met some more and kissed & talked. She then told me she had feelings for me and was thinking of leaving her boyfriend.

Which about a week later I thought she had because her whole way of her changed, she invited me round to her house and then she even stopped at mine and had sex and told me I'm in her "head and heart" and has talked about future plans with me.

So since then she has returned to more sporadic contact but still having sex with me and expressing how much she likes me. I feel like she more than likely has not left the boyfriend.

But am wondering how to approach the conversation about the elephant in the room and trying to clarifying what the deal is. I really like her but am starting to wonder if I get hurt.

What shall I do about this affair?
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