Girl Trouble!Plz help all girls!?

Ok this is long so read it all! Ok? So i am a boy. I am almost 13. I am in 7th grade. Well i am kinda having BIG girl problems. First, about a year ago this girl i was dating moved and i got really sad. LIKE A LOT. And we had this little group. It was me(boy) then a girl named Alex, and another girl named Kelsey and Miriam (girl who moved). Well after Miriam moved we kinda stopped hanging out during summer. Then this year we started hanging out again, but (this is were it gets confusing) i start to get feeling about Alex(me and Alex were REALLY good friends like A LOT) I started to get these feelings. I put them off for a while. Then a week ago Alex had her Bat Mitvah. And i was like the last person at the after party. Wait i am getting ahead of my self. Well there was alot of people there. And we were all dancing. Like to fast songs. Then some people left. Then some more. Then there was 6 of us. 2 8th graders. Sammy(Alex's bro) who is like in 5th, Betty(Alex's friend) and me and Alex. And then we started to do some slow songs. And the 2 8th graders danced. Betty and Sammy started dancing. And then it was just me and Alex. So i asked if i could have this dance (like a gentlemen) she said yes. Then we started dancing and i started to look into her eyes(this is really mushy) and i got those feeling again. But this time they were really strong LIKE A LOT. and btw my gf for a year agoMiriam was at the Bat Mitzvah. She came from California for this. And i actually spent the whole day with her. For 9:30Am to 12:30Am. And i went home at 12:30 and i was the last one there except for Betty who was sleeping over. I gave Alex another hug and left. I have been thinking a lot about her, and that dance we had. And all week i kept looking for her and saying hi and giving her hugs. I have no idea what this means and if u read this far thx. Plz help me. I dont know whats up. I have never had this feeling about a girl before. I am posting this again cause i need a lot of help!