Your problem may be pushing it way too soon.  Doing 2x the work you did last week will not make you 2x better.  The body just doesn't operate to function better that way.  A better solution may be in looking at your total weekly time, and increasing that by just 5 to 10%.  So, lets say your running time is 50 minutes total a week, with 5, 10 minute runs, try 5, 11 minute runs the next week.  This won't be such a jump & a spike.  With the marathon in October, you have a good 4+ months to prepare, so don't try to jump up in mileage too early.  Smooth, steady increases in volume will help you, while sharp doubling of workout volume will tank you quickly.

Just some thoughts & observations,

Rick Karboviak, CSCS

www.thetipedge.com

Hey don't worry about other people do what feels good, not everyone has the same training regiment and don't over run yourself where you get bored or burn out. You think your over weight are you kidding me, I'm 5'7" and I weight about 195 I'm a bit muscular so I factor that muscle are heavy. But I been training for my fourth marathon the one in San Diego (r&r) this June and I got one more long run this friday (11.5) then I will start tapering off. About your weight you will loose it while you are on training by the time I run the marathon I will weight about 175 or less. You have a long time before October so take your time, gradually increase your mileage slowly and you don't even have to run everyday this is how you get burn out. I run (3) days straight about 6 miles then a day off and on the weekends is when I do a long run which is about 11-13 miles, but I take 2 days off to run the long run. 2 1/2 months before the marathon thats when I start gradualy increasing my mileage from 13 to 17 then 20 to 23 or 24.5 then two weeks before the marathon I will start tapering off. Just do your own training that feels good to you everybody is different. My way of training might not work for you but it work for me and run on your own pace. After the one in June I have another on December so I'm always running even if I'm not training for the marathon I always run 10-13 miles on the weekend plus do some small races like 5k and 10k this is a good way to get out off a rut. Well good luck to you keep me inform on your training..

Sounds like you're a beginning runner with no mileage base under your belt. I wouldn't start with a marathon as my first goal race.  I would consider finding a 15K or half-marathon race to start training for.  You're going to end up getting injured or having a terrible time on your first marathon.