Middlegame plan
You are playing London system & caro kann. Study the typical plans of those systems. Start with London, it's easier to learn.
Tip: your opponents are playing wildly. Don't be shy to throw some counter-punches. You are playing too timidly even when your opponents are playing wildly & badly.
For example: if your opponent's king is in the centre, and he is playing f or g pawn, then open the centre and attack his king.
yes learning opening theory can help quite a bit. you should know weak points, important squares, lines, which pieces are most important in the most various openings and how to use them. there is only onw way to do this. it is to study your given openings deeply either through chessbase DVDs or through books.