It's ok and thank you for all of your support/help. My mother and I were very sad. Since it was a gift for me, I felt like I had caused his sickness which lead to his passing. After a while I accepted the fact that there wasn't anything I could do.
However, we are going to purchase another betta in the summer. Two of my friends have bettas so I am gaining knowledge from them and this site. Anyway, I hope I will have better luck next time..
Sorry to hear that your little guy didn't make it. Sounds like you did the best you could for him, but sometimes it happens (even when you've done everything right)
Hopefully, you can set up your tank again when you're ready, get a little heater and give another betta a good home.