Is Your Boyfriend Interested in Someone Else? Signs & What to Do

Question
how can i know if my boyfriend likes another girl but he said that he loves me so much?

Answer
Please keep in mind that I am not a relationship expert, so I just giving my opinion on this particular subject.
If your boyfriend is doing anything that makes you uncomfortable regarding another girl, then it is a big concern.  For example, if he has been flirty with her, and you have told him that you do not like that, and he has not shown you the respect you deserve and stopped the flirting, then maybe he still loves you, but not as strongly as you need.
If you are in a short-term relationship, you can probably overcome these type of problems.  If you think it will be a long-term or even permanent relationship (between you and your boyfriend), then you need to sit down and calmly (not arguing) tell him what you need from him, including specifically how he acts towards other girls.
I hope all works out all right for you.  Remember that you are very important, and if your relationship with him works out, that is great, but if it doesn't, even though it can seem very bad, it very well may be that a better relationship is heading your way in the future.  Stay calm, rational, and be the best person you can be.

Also regarding your question, he may like another girl, but it depends on how he likes her.  If his feelings toward her are as if he and her were boyfriend/girlfriend, you need to evaluate what is best for you.  Talk with him first.

I wish you all the best.