Root canal or not?

Hi! I'm going to be honest here... I haven't been taking care of my teeth like I am supposed to. Plus I've been eating and drinking a lot of unhealthy snacks.
Some time ago I noticed a big hole in my tooth. I was like "no biggie, a filling fell out. I have an appointment anyway so she will see it and fix it". So yesterday I came back from the dentist. She was driling and driling in my tooth, and she told me it was fairly deep. As you can guess, it wasn't just the case of a missing filling. Something bad was happening. But I didn't feel any pain before coming to the dentist. So, my first question - is it bad that I didn't feel any pain? Does that mean my tooth is dead?
After a couple of round of drilling, I felt pain and flinched. The dentist said she was glad I felt something, becauese that meant root canal wasn't needed, but she can't do the rest of the procedure now, because there's too much blood, and that I should come back on Monday. Here is my second question - will I need a root canal anyway? I'm terrified, I know it's my fault, but I'm only 18 and I don't want my teeth to be "fake".