Win streaks and loss streaks are common, but are not related to your actual skill rating or MMR. Naturally of course the higher you climb the more difficult the matches will get (that is the point of a ranked ladder of any competitive game). It’s also not uncommon to ride on your emotions (get energized when you win, get tilted when you lose). Anyone who says there are “forced wins or losses” in Overwatch are fooling themselves.
Here is a handy detailed guide to matchmaking and skill rating in Competitive Overwatch.