When ever I search, random adverts fill up my page and random search engines come up?

When ever I search, random adverts fill up my page and random search engines come up?

It's been a recent problem, whenever I search I get random pages, such as adverts and these search engines appear, my internet has recently been slow too, I'm not too sure if this is related.
The problems a little hard to describe, but your help will be appreciated, as it's really bugging me.
Thanks.