It's normal to get in the mood and be interested in boys.

sexual desire and masturbation are normal. whatever age you are.

in my view though you are still too young to be engaging in this sort of stuff though. you are still a minor. i'm assuming you don't know anything about these 'boys' except for what they tell you about themselves. which could well be all lies. they could be 50 year olds for all you know. you are putting yourself at risk for paedophiles and perverts to prey on you. or encouraging them to prey on other people for that matter.

at 13 you are growing, but you are by no means developed. there are lots of ways you can experiment with yourself and your sexuality at your age without engaging with other people. i think carrying on with this behavious is at best going to embarrass you (when someone finds out) or at worst going to get you really hurt.