I have been haveing some trouble after the merge. I like to make a long sweeping climb to the left.
And that's your problem.
You shouldn't have moves you do because you "like" them; you should perform maneuvers that either
1) make it impossible for your opponent to follow through without putting themselves at a disadvantage
2) neutralize any advantages your opponent might possess, allowing for a neutral secondary or even tertiary merge, or
3) respond directly and appropriately to your opponent's maneuvering in a way that his advantage is minimized, if the above two options are not possible.
Those are the only options, in that order, you should be pursuing during and after the merge.
In practice, it's not complex. Following the flow above might be as simple as performing a maximum-rate Immelman... or maybe a flat-turn. The point is that you never, ever just do a maneuver "because I like it," or "because I've had good success with it," or for any other personally-subjective reason. The only maneuvers you should be performing are those that apply specifically to your situation.
A phrase I use a lot in pilot training applies here:
If you can't explain why you're doing the maneuver, then you shouldn't be doing it.The point is that is you can't explain why you're doing the maneuver (even if it is the right maneuver to perform), then you don't fundamentally grasp what's going on around you. You need to fully understand the maneuvers, why they're used, why they're effective, and when to use them in order to apply them successfully. Otherwise, you're simply flying by the seat of your pants.