I think I love him?

So hi I'm Mariah and I really like this guy named Alex he is my best friend and I have a lot of feelings for him like we got a lot in common and like even tho he can lower myself esteem sometimes I really care for him like no matter what and I think I love him every time I see him and we talk I'm always so happy but then when another girl is like talking to him I kinda get jealous and like I want to tell him but what if it ruins my friendship ? I don't want to lose my best friend because I secretly love him (I think)