Hi.
i am exacty the same, i started cycling 3 years ago and have stopped and started a dozen times.
I tend to start, cycle 3-4 times a week, get fitter and faster for a couple of months then it starts, miss a planned ride thinking ill do it tomorrow. before you know it a week has gone by then 4 months.
Then i get the bug again and have to start from scratch, everytime i start i struggle to do 20 miles at 12mph and build up to about 30-40 miles at 15mph and never get any further because i stop going.
Ive been back on the bike about a month, this last week has been my best ever only missed 2 days out of the last 10.
the secret? i bought a bkool trainer, its ideal for using on weekdays when ive only got an hour or so then i can get out on the bike for 2-3 hours on a weekend.
hopefully i will stick at it this time. If you dont wish to use a virtual trainer your only other option is to gear up and get out in the dark