To start as the others have said, You're not stupid!!! Everyone gets lumps to start with!
I listened to the MW with DD#1 and only fed her 1 boob per feed, against what my mother was telling me (who BF twins then me).... Got to about day 7 then T was very unsettled, got worse and worse, she didn't sleep a couple of nights... My mum was telling to give her the other boob but I kept telling her things have changed in the 20 years she hadn't been feeding for! Day 14 came aroun and it was time for the comm nurse to visit.... I had been starving my poor baby!!! She was starving!!! She definately needed that second boob! I felt even worse because I had been expressing the 2nd boob as it was so enlarged and killing me when I should have been feeding her with it that whole time.
DD#2 came along and I fed her both boobs from the very first feed. Once again the MW told me not to, but I explained to her what had happened before and I would do what I feel is best.... H has never been left starving!!!

Massage and maybe some expressing (just a little to releave the discomfort) will get those lumps out. Do what works for you! It's all trial and error dear