Betta Fish Care- What kind of sickness is this?

I've have my betta Momo for little over a month now and he's been a happy fish. He made a bubble nest and all. Well after I changed his bowl the first time he seemed okay and he ate fine. Then last week he started to swim around less and eat less (which was odd for him considering that this fish liked to eat and was constantly moving around even following my finger). Over the weekend he started to slink towards the bottom of the fish bowl and lay there. I thought it was his water so I changed his water again. He started to staay more towards the top of the water now and get some of his energy back, but he's still not eating, not really energetic , and he has these red almost bump/spot looking things at the end of his fins. I looked it up everywhere and couldn't find anything and I called petsmart (where I got the fish) but they said that if something happened to my fish there's always more. Can anyone help me?