Mac is running very slow

Hello all, up to a few days ago my Mac would take about 3-5 mins to boot up and load. With that it used to perform very well, open multiple browser tabs and open multiple apps with pretty good performance.

But recently it got drastically slower, takes a much much longer time to boot up and to just load the browser takes more than 5 mins and everything is incredibly slow.

i cleared the system cache, deleted startup programs and cleared up programs running in the background but this only helped minimally.

what else can I do????

2011 MacBook Pro

2.3 GHz i5

8 gigs Ram

100 gigs free hard drive