Is it normal to react like this?

I am kinda the same way lol. If someone doesnt reply back after a period of time, I start to wonder myself lol

It's normal, since you really cant control the internet. And peoples lives.

What Ive taught myself though, is to be patient for them to respond.

My sister is like this with her boyfriend, if he doesn't reply straight away she thinks he's ignoring her, and even when he replies if he doesn't put kisses at the end it means he doesn't love her, and she starts crying. She's 25 btw.

It's true. "You young people don't seem to have any patience ...and get angry quicker if they don't get a response in a day or 3. I'll always wonder why we men don't develop emotional intelligence and understanding earlier, e.g. I remember leaving pretty bad messages with girls/women that turned me on ( intellectually, too.) I often wonder why I didn't have the smarts and patience to play relationships, especially during the first few 8-11 months with calm patience. One told me than I was dealing with someone more emotionally mature than I ...One told me, I 'll never forget,"we bring out the worst in each other.." which was just plain horseshit. She and I both wanted long term intimacy, but in retrospect was more frightened than I.
Main point: Forget the rude, stupid,hypersensitive responses you got on this forum. Think about this:
."if I knew then what I know now" is a thought that's coming to you.. Sexes differ, e.g. men mature more slowly until a point. The irony is men stabilize lifelong after that, whereas some women seem to have mental pauses ( aka menopause) indefinitely. Some move to California to liberate themselves,and,destroy virtually everything that could be lasting.
The trick is DON'T try to justify your outburst as "normal"!!! Learn from it, call it age appropriate instead, and move on. Later, he/she might be sucking-up. If not, whomever never liked you in the first place, and you better have better things to do with your time!

Seems a pretty common complaint on here.
I guess if you always expect instant gratification, people are going to constantly be letting you down, especially if those people don't consider you the most important thing in their lives.
You young people don't seem to have any patience at all. When I was your age, a response to a letter mailed could take weeks or more. We never worried that the other party was upset with us or didn't like us. A reply took time. We didn't even have answering machines on our corded phones, so if we missed a call we didn't even know it. Yet we didn't freak out because we hadn't heard back, after 52.4 seconds!
Give yourself a break. Possibly, just possibly, your internet friend was taking a shit and didn't take the phone into the bathroom. That doesn't mean you did anything wrong or that he hates you. It just means he didn't take his phone into the damn bathroom.