Dont waste your time doing another degree first - a) it'll take you 8+ years to get a Medicine degree and b) you'll have to fund most of the 5 year Medicine degree yourself, so not a good idea. If you REALLY want to do Medicine, dont settle for anything less.
Whilst most Med Schools have a 'no retakes' rule (ie. they want people who dont need a second run up) they usually will take circumstances like this into consideration. If you genuinely couldn't do the right subjects in one 2 year period at your school, then email some Unis and ask if they will still consider you. An attached letter from your school confirming your story will help.