Help me understand matchmaking please.

This is gonna be a QQ thread I guess, because I am becoming depressed over the game.

I try not to feed, I help my teammates, if I mid, I usually go even or somehow fed, but even if I do get fed I'm not sure how to carry from that position, but it always seems like its up to me, and that's intimidating.

Everyone on my team is always losing by a landslide against the opponent, its like my opponent is always better than my teammates, why is this??? What's going on? I'm getting really sick to the point of nausea every time I hear first blood.

I know the laning phase is just the laning phase, so in a regular game if someone gives first blood, its not end all be all, but when everyone is dying over and over and over without getting anything done, I just don't know what to do other than my best. This has been a regular thing for the past few days. Does the game expect me to play like a challenger to climb? I like to think im a bit above average in my current mmr, but that doesn't seem to be enough.

What I imagine it's supposed to be, is that I should be matched with similar skill vs similar skill. I don't mind if I don't get fed or if I fall behind because I know how to play from behind at least, I'm not saying I'm super great and everyone sucks but me, and I recognize that I am not going to win every single game. But matchmaking seems like matching me with just below skill level of opponent team.