Pretty much agree with all the comments above. Don't spoil your potential enjoyment of your new bike by thinking you need to be at a certain level of fitness by a certain stage. Take time to enjoy the scenery you are riding through and not be a slave to big mileages. You have identified that you needed to improve your fitness, and buying a bike is a great big step in the right direction, but...........Rome wasn't built in a day!!
As suggested, it may be worth getting a check over by your GP, but I'd be willing to bet that you probably just over did it on those first couple of rides, especially if you are a bit out of condition.
Do you have a mate or two you can go riding with? A bit of idle chat and banter while out on the road will help to divert your attention from how bad you "think" it is going.
Sound advice from the guys above....... Start small, work up to better fitness and more mileage...........but whatever happens, enjoy it!!!
