She says she loves me but isn't in love with me. Says she needs to see if there is something better. She's meet someone on one of those dating sites and is going to meet them and she wants to know if I will still love her and still have her if she finds that there isn't better and I am the one. We've been together for almost 10 years we have 4children one together one I had from previous and two she had from previous. . I am so confused

She means, I think, one of two things: either she has a childish vision of love that doesn't go past romantic love, or she feels that something is missing from your relationship in terms of how you show love to her. The second one is very common, usually in women, who tend to need to be shown and told that they are loved on a regular and ongoing basis, whereas men tend to think it's 'understood' and doesn't need to be expressed. Men also have a tendency to eventually treat women as their mothers - you provide, they maintain the home and care for the children and feed you and clean up after you. If you aren't throwing some little surprises into the mix several times a week, even a minute or two of sneaking up on her to hug and kiss her and tell her how great she looks, or bringing her flowers or telling her how much you appreciate all she does, then you fit the stereotype of the thoughtless male, and she of the woman who can't tell you what she needs and wants.
Try to think of 10 little moments of love this week. Who knows what she will do? Maybe she won't want anyone else.

Thank you :but what do you mean by (10little moments) we've already established 3 rules :rule 1 no more talking about the past as it is the sorce of all our endless circle of blame :rule2 we agreed on a safe word for when one of us.begins to feel angry :rule 3: spend one hour a day with each othe out outside the home just the two of us

I would say go to professional counseling, each person has their idea of what and how they show love to the other. You may in your way be showing her you love her, but she does not see it, and/or does not believe you see it from her. Communication is normally the biggest issue.

I gave you some 1 minute ideas. Do I have to make a list?
Say WOW you still have it babe as she's getting dressed.
Hug and kiss when she's cooking, doing dishes, laundry.
Your hair looks good this way!
You're the smartest woman I know, and beautiful too.
I stopped along the road for wildflowers because they remind me of you.
With a mother like you, the kids are going to turn out OK.
Why can't you think of anything? Oh my oh my