Plugin works but breaks Admin Console

This is so wierd. I’m fairly new to WordPress. I created my first plugin.. basically allows me to put a PayPal Buynow button/function on a page using text trigger (I know there are many plugins out there that already do this)… My plugin works perfectly however once I activate it, my Admin Console has an issue refreshing after I apply any update… e.g. if I go to any page and make a simple change, then update… my browser screen clears but never refreshes.. it just hangs. If I close the browser session and then go to the Admin screen, I see that my change DID take affect…
If I disable my plugin, then Admin Console works properly e.g. if I make a change to a page the browser session clears and refreshes.. and does not hang…
.. so what have I done???