I've been cycling for 8 months ...,. my 1st ride was 3 miles and I struggled to breathe.
I've now lost over 40 pounds, and ride long distance at speed and I pass many who wear lycra and dress like Robin Hood.... my longest ride was 119 miles at a good pace, and I average just over 200 miles per week (I commute by bike and work at several sites every day):
https://www.strava.com/athletes/12571658
here is my advice:
firstly, sign up to Strava ... it's for free (I have the premium membership which costs £4 a month and gives some extra details) .... this will log your rides and you can see your progress
get a bike computer that has cadence (RPM) .... try and ride at 80 RPM on the flat roads ... use to gears to get this
ride 5 consecutive days in a row and increase your distance every week .... on your rides, choose a section where you ride as fast as you can (for a few minutes), then slack off to get your breath back (high intesity training)
the first 2 weeks of doing this, you will be sore, and I tossed and turned at night when I slept, but remember that if your legs don't hurt after cycling, you never tried hard enough
eat proper and cut alcohol (if you do enjoy a drink, have them on your rest days)
you will be amazed at how fast you get fit .... what you put in, is what you get out
