Okay the type of work you discribe is crazy considering you are not arobicly fit. by the sound of it. getting fit takes time, you need a sound base to work from which at the moment you havent got. To get it takes time, all you should be doing at the moment is steady state work to biuld your arobic tollerence to a level that you wont injure yourself. all you should be trying for is to feel good. then take it a step at a time, longish walks to start no impact nice little stretch routines, get into a bike spinning class start slow finnish fast. remember the saying no pain no gain, biggest load of bollocks ever spoken.