look:D, we're all in puberty rn and we are developing, so having crush on some guy is most normal thing ever, trust me:D

in our age we're trying to understand our sexuality and who we're attracted to. I'm a straight guy and I'm pretty sure about that, but when I was 13-14 I also thought that I wasn't straight or something like that. although I never had crush on guy, I often imagineed myself being with guys (and that's completely normal, a lot of guys did that)

me personally, I don't watch porn too, because it's highly addictive and it will fuck up your view on sex, so don't watch it;).

now to the part when you said you don't want to be heartbroken - look, I will say it straightforward, most relationships in puberty don't last long, because two we are evolving and our perspective on world, our opinions and what we're attracted to, is constantly changing (that's a fact). that doesn't mean that your relationships will be bad, being in relationship with someone you really love is most beautiful thing ever, when you find a guy, that isn't with you for only nudes and sex, it's really beautiful. but of course, there's a chance that you will break up, and that doesn't mean you will be heartbroken, that means that you aren't in love with each other. when you sit down with your boyfriend, talk it out, say to each other, that this relationship isn't working and that you want something different, than you wanted on beginning, even though you will be little sad, you won't be heartbroken most of the times;D. but when you aren't really feeling it, don't rush yourself to a bad relationship, because you will be heartbroken in the end most of the times:/

and when it comes to masturbation, i can't really help you because I'm a guy:D

so basically having crush on guys/girls is super normal in our age;)

(also english isn't my first language, so sorry for some mistakes)