Really SLOW Internet via WiFi

Hello,

I have been experiencing slow internet for a couple of months now making it frustrating to do anything online.  Nothing changed on my end that I am aware of.  I went on vacation and when I came back, my internet issues started.  I am not a heavy user and do not have a lot of devices connected.  Even so, I am getting download speeds mostly in the 20 - 200 range and upload speeds between 10 - 20.  I have contact Xfinity by phone and have had two tech visits.  Nothing has improved the speeds, buffering, dropped connections, etc.  I am not sure what else to do, other than explore changing to another provider.  My purchased router is just a year old, and I use extenders.  I can buy a new router but I have no confidence that this will fix my issues since the one I have is relatively new.  I have read through the comments and have re-started my modem, router and computer several times.  I am not tech savvy at all, unfortunately.  Does anyone have any suggestions as to what more i can do to try to figure out the cause?  I would appreciate any advice.