well pump won't turn off

i have a pump which has two pipes coming into it and one going out to a small pressure tank.

my issue is the pump will kick on but it will not turn off. i havent' adjusted the switch from last year.

if i turn the power off to the tank the presure will hold at approx 40psi but it will not go over that when the pump is on. so the pump will keep running on and on without shutting off because it will not hit the 50psi shutoff

any suggestions?