I lost so matches one year, I got dropped a level. From what I have seen since, that is really hard to do because even if you are competitive at a level, but lose your matches, you will computer rated at that level.
Which is the way it should be, it's a skill level, not a win/loss level.
Especially in the OP's situation, he's playing doubles with 5 different partners. There are all sorts of factors that go into that to complicate things (along with the variety of his opponents), a lot of which dont necessarily have anything to do with his ability to play tennis.
Sometimes teams are just good at losing. They will give you a competitive match and you'll have to fight to beat them but somehow they find a way to not pull it out because it's not all that easy to actually win a match sometimes.
Normally when I see teams mixing and matching partners, they lose tons of matches because of that.
When you see entire teams that do really well it means one of three things:
1) Either they have highly skilled competition that are not competitive with the rest of their league
2) They use the same partners on most weeks rather then mix and match, so you see them as a "team" and not just two guys playing tennis together.
3) They have been around for a long time and even though they may mix and match partners they all know each other very well anyway because they've played a lot of tennis together.
Especially at 3.0 and 3.5 where not everyone plays perfect doubles strategy so you have to waste time every week getting to know your partner in the match and try to work with whatever weaknesses or strategy flaws that they might have.
Not the mention the mental aspect of having to deal with a whole other person from week to week. In singles it's hard enough to manage yourself when the match gets tight, but in doubles it's even harder because there is this whole other person on the court that can affect your mood.
