There's no twitching, scratching, spots or anything just heavy breathing and resting on the bottom, I was hesitant to give him a freshwater dip incase it stressed him out anymore.
I would strongly recommend the FW dip. It's minimally invasive and easy to do. Everybody is always freaked out when they do their first one. I've done literally hundreds of them and can tell you that it's easier on the fish than you think.
Freshwater Dip: Provides temporary relief for Brooklynella, Flukes & "Black Ich", Marine Velvet disease (Amyloodinium); possibly even Ich & Uronema marinum (both unproven). Can be used to confirm the presence of Flukes.
How To Treat - Fill a bucket with RODI water, and use a heater to match the temperature to the water the fish is coming from. Aerate the water heavily for at least 30 minutes prior to doing the dip, then discontinue aeration while performing the dip. Fish aren’t overly pH sensitive for short durations like this, but you can squirt a little tank water into the dip just before the fish goes in to help bring it up.
Place the fish in the freshwater (FW) dip and observe closely. It is not unusual for them to freak out a little at first. Also, tangs are notorious for “playing dead” during a FW dip. The important thing is to watch their gills; they should be breathing heavily at all times during the dip. If breathing slows, it’s time to exit the dip. Dip the fish for no longer than 5 minutes. Multiple dips may be done, but it’s important to give your fish a day to recuperate in-between dips.
For flukes, use a dark (preferably black) bucket so you can see if tiny white worms fall out of the fish (especially out of the gills) at around the 3-4 minute mark. The worms will settle to the bottom, so you can use a flashlight to look for them there as well.
Pros - Provides temporary relief for a wide range of diseases in a chemical free environment. Can “buy you more time” until a proper treatment can be done.
Cons/Side Effects - Not a permanent “fix” for any disease, as FW dips are not potent enough to eradicate
all of the parasites/worms afflicting the fish. Some fish can have an adverse reaction to a FW dip by appearing unable to maintain their equilibrium once returned to the aquarium. If this happens, hold the fish upright (using latex, nitrile or rubber gloves), and gently glide him through the water (to get saltwater flowing through the gills again). It is also a good idea to place the fish in an acclimation box until he appears “normal”.
This will confirm/rule out flukes and possibly flush out the gills so he can breathe better. A few hours after the dip, you'll want to observe from a safe distance and see if his breathing has improved/slowed down to normal. If you didn't see any flukes in the dip and the breathing has improved after then we need to look at other causes like Ick in the gills. For now, this link has pictures of what you'll want to look for in the dip. (for some reason I can't copy and paste my own pictures - stupid computer)
https://www.reef2reef.com/threads/freshwater-dip.248898/
I still put him in freshwater but I don't think I could see anything unusual. The only thing I can think maybe the acclimatise. I tested the water again and ammonia and nitrite was untraceable. I'll drain and clean the tank as a precaution. 
