Be advised that medals only compare your stats to that of the rest of your team in each match. Performance based ratings are your stats compared to other players in other matches that played the same heroes you did in their matches.
This really sounds like you are on track to regaining your true skill level. Yes it will take time and it may not feel too good to start lower than what you may remember, but that is the system working to make sure the top ranks of competitive play remain at the highest level of competition (remember Diamond and higher account for less than 10% of the entire player population). This post really takes time to explain all of the nuances of skill rating adjustments and is worth the read if you have more questions: