Friends with benefits

Hi all, I've never posted here before so I don't know how it works. To maintain anonymity I will be changing names in my story. I am a 21 year old uni student and Anna and Lucy are as well. For the past 2 years I have been in a friends with benefits relationshop with a girl called Lucy. She's nice and I like her but I don't want a girlfriend, just benefits. When we met she had just gotten out if a relationship and when we started our fwb we both agreed it'd just be a fwb thing and that we were free to see others if we wanted but that we had to tell the other person. About a year into our fwb relationship I suggested we try being a couple. I wasn't sure if this was what I wanted so we kept it to ourselves and didn't tell anyone. After 3 weeks I decided I didn't want to be in the relationship so I ended it and we went back to fwb. She was upset about breaking up but was happy to continue as a fwb. We talk every day and have been away on holiday together and spend heaps of time together so in every respect we may appear to be a girlfriend/boyfriend couple but we're not. A couple of months ago another friend of mine, who's name is Anna, broke up with her 3 year boyfriend. Anna is known to Lucy but is not good friends with her. I have known Anna has had a crush on me since I started my fwb with Lucy and I have had a crush on her as well but never said anything because she was in a relationship. Now that Anna is out of her relationship she came to me and confessed her crush. We hung out a couple of times and kissed once. After the kiss I told Lucy, as per the terms of our fwb relationship, and she took it really badly and told me I was a jerk for doing it because she had feelings for me. She had never discussed these although it could have been argued it was obvious. At this time I assumed our relationship was still fwb and that we were open to see others. Lucy then ended the fwb part of our relationship and told me that we can still be friends but if I wanted to sleep with her I had to date her. However she also said if I had sex with Anna we could not be friends. Recently I have had Anna come to me and ask if I wanted to have sex with her. Anna does not know about my fwb relationship with Lucy. I want to have sex with Anna but I also want to continue my friendship with Lucy. I am comfortable not having sex with Lucy and I understand her position but I want to have sex with someone and I'm not sure if it's fair for Lucy to be telling me who I can and can't sleep with. She has said I can sleep with anyone I want now except Anna. My question I would like help with is - do I sleep with Anna and tell Lucy that if she doesn't like it that's her problem or am I obliged to respect her wishes and sleep with any girl except Anna?

Thanks for your reply Susan. I do not want to be in an exclusive relationship at the moment. I have always made this clear to Lucy (except for the brief period we did date) but haven't discussed it with Anna. I believe you are right in saying that both girls want an exclusive relationship. Lucy definitely, because she has told me so. Anna I suspect but I haven't actually spoken to her about it. So far she has only said she wants to sleep with me. Health issues aside for the moment, when it comes to sleeping around I always make it clear when I start sleeping with someone what the terms of the relationship are. If sex is just sex and nothing more meaningful then I make that known before we do it. The problem that has arised here is that sex became something more meaningful for Lucy at some stage in our fwb relationship and it wasn't talked about until too late. I have considered that I am using Lucy. It has been two months since we last slept together and we still hang out constantly and talk as much as we ever did. Given that we are no longer sleeping together I do not think that me using her is a concern anymore. I haven't spoken with Anna in terms of what she wants. So far she has just indicated sex but I suspect she wants something more, in which case I probably shouldn't start anything with her. So thank you for your advice there. I also agree that despite what she says,lucy probably won't be comfortable with me sleeping with any girl but it's going to have to happen eventually, right?