Questions about Marijuana and smoking

I've been smoking for about 3 years now and there's a few things I've always wondered.

I started out smoking on weekends and now I smoke probably 4-5 days of the week. Out of all this I've greened out once, while it was a terrible experience it was also an interesting one.

The reason I bring up the green out is because when I did green out I smoked less than I usually do. However I had 3 days off work so I decided to spend those 3 days at a buddies house. We smoked pretty much all day everyday without eating barely anything at all, come the third day I greened out after a Lung hit, a bong hit and a couple joint hits.

This leads to my question, could I have greened out because of all the THC in my system and no food? Does smoking work the same way as alcohol? (Less food = fucked up faster)

Since that day I swear my tolerance for weed has gone lower, after 3-4 hits of whatever it is I'm good for a couple hours. But even those 4 hits has me feeling somewhat sick unless it's just my mind. I'll be sitting there doing whatever and I'll notice my stomach/body starting to feel weird, and when I do noticed it I get freaked out and worry that I'm gonna green out again.

I usually just get a drink of water and try my hardest to not think of it, and every single time this has worked. Then I go back to a normal enjoyable high.

Sorry for such a lengthy post, I really enjoy writing