I have no idea how many calories anything is...

I just started writing it down today, but I know I've cut back a lot.
I've been trying to eat things I know are low in calories and fat. Tuna, veggies, oatmeal and such. I'm a sucker for a bagel, though, and potatoes are the devil. I don't really like red meat and I hate bacon, so I'm not sure what other protein options I have... I guess I'm playing it by ear. That's why I need your help. LOL.
When it comes down to it, numbers confuse me. I'm hoping carrying a notebook will help me keep it somewhat in check.