ride getting harder

[wardy_uk]

I'd echo the comments that its probably not that your over training - but you could get more out of your 5 miles and still feel less knackered... Look up HIITs (high intensity interval training) you do short burst tanking it then slow right off... The repeat... You'll get fitter quicker and loose weight quicker..

For an idea of effectiveness, Roger Bannister used this method to train... Albeit not on a bike... But we all know how that turned out