Losing a lot in all kinds of time controls… Advices?

Chose 1 time control e.g. 15|10 and play that exclusively. Whenever you change time control you either play too fast with too many mistakes or too slow losing on time.
Whenever you lose a game, stop playing and analyse it first so as to learn from your loss as the imprint is still fresh and to channel the negative emotions of the loss towards a positive goal: improving.