ugh im in big trouble T_T
I seriously doubt it. It is not illegal to connect to a tracker, (or even to download movies and music, in some countries). More likely a "pay up or else scam" and almost certainly you were not contacted by federal authorities over the phone. If they want you, they will knock on your door. Normally I would say ignore this but to be on the safe side you might want to contact a lawyer, just for your own peace of mind. Personally I would highly suggest using a proxy to connect to trackers in the future. Try contacting the EFF at
https://www.eff.org/ other than that I would strongly suggest going about business pretty much as usual.
Most of these "scams" come from fake or dummy torrents setup to catch IP addresses from downloaders. This is not something they would want to come out in court as it would mean they have no case, (intent to download is not against the law, unless it is clearly described as childporn, in which case someone would have come for you already). Try to be a little discerning who you download from, anyone posting for the first time or who hasn't a history of reliable torrents is a risk.
It is not widely known but the porn industry spends more on anti-P2P efforts and lawsuits than any other media industry. They are in it soley for the money and you are in no danger as far as I can tell. I have never heard of a publicized settlement of any worth for downloading porn. Don't give them a dime and tell them if they call again, (how in hell did they get your phone number anyway? I think your sister was putting you on for the giggles), that if they continue to harass you in anyway you will sue them. You would likely win to.