Is it normal i'm still freaked out over something i did 5 years ago?

Unless they were threatening you have nothing to worry about. Even now if its been 5 years if you're in the US that's over the statue of limitations and you can not be charged.

You being upset by what he did is understandable. It's also understandable that you acted on the urge to get back at him, and you could have done a hell of a lot worse things than prank calls.

But harassing someone is unwise and it's often illegal. The degree to which it's against the law depends on the legal jurisdiction it happened in, how long it went on and what exactly was said in the calls. A single prank call is very different to twenty calls a day for a month. An obviously automated jokey prank call is very different to a call where someone who says he's a member of a Mexican drug cartel addresses the target by name, cites his address and says he's going to burn his house down.

In most places, there's something called the statute of limitations which sets a maximum amount of time between when a crime has occurred and when someone can be tried for that crime. The rules vary, and very serious crimes (murder, kidnapping, sexual assault of a minor, etc.) are usually excluded, so they can be tried many decades after the event. However, in the grand scale of things, what you did was pretty petty, I suspect that means it would be classed as a misdemeanour, and that probably means you can no longer be charged.

However, I wonder if you actually ever got a call from the cops in the first place. If your ex did really contact them, then it's possible they might have decided to give you a scare by telling you they were investigating and then did nothing more. If they had actually treated his complaint seriously, they would have sent a cop to your place to have a little chat. It seems more likely to me that if he had got in touch with the police, they would have essentially told him to man the fuck up and piss off because they had more serious things to spend their time on. It seems to me entirely possible that the "cop" you spoke to wasn't a cop at all, but some dickhead buddy of your dickhead ex who was prank-calling you right back.

Since you're still fretting about this, I suggest you look into what heading harassing calls come under in your local criminal code, and what the statute of limitations is for that class of crime.

Something you might want to bear in mind in the future is that the old adage about revenge being best served cold is true. Your main error here was in not waiting longer before you started pestering the asshat, so it was way too obvious who was behind the calls. If your ex is as big of a jerk as he seems to be, then you waiting six months would have probably resulted in the list of people he'd recently pissed off being so long that he'd have no idea it was you. Also, if you're going to do this shit, you need to put some thought into staying untraceable. I don't know how it works where you live, but in the UK you can buy mobile SIM cards for cash and top them up with cash, and used smartphones are cheap. It's very challenging for law enforcement to link any internet activity on such a phone to a particular individual, and they sure as hell wouldn't even bother with something as trivial as prank calls.

I think you can assume he's moved on and you're safe.

He's not going to press charges. Chances are he stopped caring about all of this long ago and doesn't even think of you anymore. It's best to let this go.

Living in the past makes no sense. Let it go.

It’s not even illegal unless you threatened him. What did you say? As a frequent ex boyfriend cat fisher, you just have to be careful about what you say.