Why do I get such inconsistently bad XP?

It seems as if every time I get on MCC the amount of XP I get every match is completely different and most recently it has been the worst by far. A while ago I could get matches that cap my performance XP at like 24k (I am assuming this was a double XP event). But after this the default max XP was almost always 12k, that was the usual, then somewhat recently I was getting within the ranges of 5k-10k XP each match (which seemed pretty normal), now, and I am playing and doing just as well in every match, I am only getting somewhere between 1k-5k XP! I just finished a match with Big Team Battle Match with 14 kills and at least 5 different types of medals and I got only 2.5k XP! What am I doing wrong? I am just trying to have fun progressing the Halo: Reach rewards and it seems like the longer I play this game the less I get rewarded for playing it… Also, I haven’t left any matches and I have only accidentally betrayed like 2 people in total over like 6 matches so it isn’t a punishment thing I think either. The only thing that I have done recently is signing up for Halo Insider, but that wouldn’t lower my XP gains, would it?