Hi, I'm 42 and have been running consistently for the last 6 years and the last few years my performances have been 5k - 18:47 and 10k 39 mins etc. Up until my Marathon several weeks ago I was running well, 4-5 mile reps at 6 min/mile pace and doing good tempo and long runs. After my Marathon, that I completed in 3:23, I am finding it really hard to run at all. Despite feeling healthy and fit, although do feel a bit tired, for the last few weeks I'm getting massively out of breath just running one mile at a steady pace. I've noticed even at rest I am breathing more than usual. The thing is, before this issue my breathing was always pretty light, in fact I've had a few people ask me "are you breathing?" when I've been running. Three weeks ago I started topping up my iron levels in case I have an issue with that but I haven't seen any improvement. Does anyone have any ideas or has anyone experienced this? I'm wondering if I should see my Doc, however I'd feel pretty stupid asking about a fitness issue when I otherwise feel fine.