I had diverticulitis in my 20s, never saw a Dr because I'm too cheap to pay for one, so I fixed it myself.
I cleaned out my guts with copious amounts of prune juice once a week for 3 or 4 weeks, then twice a month, then once a month for a few months, then every few months and so on until I felt it was pretty much cleared up.
In the mean time, stop eating pizza, or anything with bread. It's like putting gum in the gears of your cuckoo clock.
Eat lots of green leafy veggies and less meat. Don't have to go all out wacky vegan, but just cool it for a while. Also increase your nut consumption, almonds, walnuts, etc. Peanuts aren't nuts and can gum you up too.
No sugar like sodapop, Lemon water only! Especially with meals, it helps aid digestion. Diverticulitis is inflammation and can be fixed with proper diet. Bread, cakes, pasta, sugary stuff..
Final tip, Get yourself a juicer or blend up smoothies at least once daily.
Had the prob for about 2 years and haven't had a prob since as long as I watch mass quantities of certain digestibles.
I got more if you want to hear it... Until then, good luck!