I am worried my woman might be a lesbian>I do not know what to do.She looks at women more than men and watches lesbian porn.She does not seem sexually interested in me.She spends more time with her female friends than me and does not want children and does not want to marry me.What should I do?

You could be reading too much into it...
I have to confess I like watching lesbian porn but am completely straight, have a boyfriend and will get married. For some women is just about fantasising - nothing else - I could never be gay or bi - I just like men in that respect. But when it comes to sexual desires - everyone's different and some people don't have fantasies but some do - everyone is different. Don't be a walkover is you suspect anything more obvious - confront her nicely - but for now just relax and enjoy! She's obviously quite sexual so why don't you try new things together or discuss your fantasies and take it in turns to fulfil each others' desires!
Lifes too short!

How old are you? How long have you been together?

This seems to be less about her sexuality and more about the relationship.

I don't know if she is lesbian, bi or straight. I do know that it sounds like she isn't into your relationship. Is there a relationship?

She apparently has made it clear that she isn't interested in some of the same things you are (marriage and children being two of them). You have to decide how much those things mean to you and if it would be better for you to move on and find someone more suitable.

You can try sitting down with her and discussing your concerns. If you do, be as open and honest as you can be and remember to listen to her thoughts and ideas too. There may be a compromise somewhere, but I will be honest that I don't think you are compatible and that she has been trying to get out of the relationship for a while.

My knee jerk response is: Find a new woman.

It does sound like she just not all that into you. As Cat1864 said, it might be time to sit her down and have a Talk; yes that is Talk with a capital T. See where you are and where you're going. IF you don't line up than the relationship might have run it's course and it might be time to let it go.

I will add that the fact that a woman finds her friends more interesting than her "man" (assuming if she's his woman, he's her man - I assume one or both has ownership papers - can you tell I find this phrase offensive?), doesn't want to have sex with "her man", watches lesbian porn and doesn't want to marry "her man" does NOT mean she's a lesbian.

It means she finds her female friends more interesting, she doesn't want to marry "her man," she enjoys the female body (and not necessarily sexually) and she doesn't enjoy sex with "her man."

I had a 4 year relationship with a woman that always commented about other women and wondered what it would be like,, so I suggested that she just live out her curiosity. She had her eye on a very beautiful lady that we were friends with and although shy at first, they began talking and spending some time together. Well they finally got together and my lady said it was spectacular. So I came home from work one evening to a candlelit table and place setting for three. The evening was amazing and then after that, my lady was amazing in bed and didn't want to pursue it any further. She had lived out her fantasy and our relationship was solid as never before. I say that if a person is comfortable enough to discuss these this with their partner and has a strong sense of self worth, these things are harmless and good for everyone involved. BTW, my lady passed away from breast cancer about 2 years after this incident. But our relationship was so strong.