Question my frame have dropped significantly recently for no apparent reason

[Riverrr.]

Nothing has changed as of my knowledge and the games I play are Rainbow Six and Overwatch. I normally get 100 frames but they have dropped to 40-50 now. Here is my DxDiag, I'm just including it because I heard it may be useful, I'm not really sure what it is. DxDiag

 

[QEPII]

It happened to me too literally 2 days after i bought my pc, this is getting really frustrating.