Slow speed - constant buffeting

My internet has been ok since I got it about 18 months ago.  (Not great). Over the last month or 2 it’s been buffering more and more.  Today it’s worse than ever.  It has buffered 8 times in less than an hour.  Using the internet thru my phone has been terrible today.  When I try to access a link, it gets stuck and I have to close and try again - sometimes a couple of times.  I ran the speed and it shows it’s VERY poor and slow.  What do I need to do to fix this or am I just seeing the way the future is headed with T-Mobiles expansion and new services?