Fps issues

So I don't have the greatest Pc in the world. Even with a cfg that lowers all my graphics I get a steady 35-40 fps. But recently my fps have been fluctuating from 1-40 fps. And it's just constant. Not staying in the high frames long enough to even play. It just goes mad. And idk why this is happening. Please if you have any idea what is happening/how to fix please help. And it may just be my pc dying, it may just be my imagination, but it seems that like even YouTube and stuff seems to be slower. Summer pretty much just started and I cannot afford a new pc till the end of summer :(

Fps issues