As a super-fit athlete in my early twenties, I used to run distances. Mostly hilly routes through coastal mountains (up to 2000ft or so). Had a couple years where I had to recover from a bad injury. Coming back, following that two years of recoveryt, it took a good year to regain most of my earlier cardio capacity, despite having maintained all of the fitness I could via methods other than running during the down-time. Still took a year. (IOW: 3mos isn't much time, starting from a modest fitness point and following a long illness.)
Depending on what your 10mos of illness was, in terms of the extent to which it impacted your cardiovascular and respiratory capacities, you will almost certainly require more time to be improving on the fitness. Adaptation to a seriously different training regimen can take awhile to become part of you.
From a cardio standpoint, you might well try rowing on a gym station three possibly four times per week. (In addition to your 20min bike commuting routes.) Half of those sessions, strive for higher-cardio interval type sessions, and half of those sessions try for longer, steadier, deeper breathing sessions (though still a challenge for cardio). If you can afford the time, I suspect that 3-4 such 20-40min cardio sessions weekly will have a markedly better impact on your cardiovascular capacity in a handful of months from now. Depending on whether any residual from your illness is still hanging around. Eat well, with highly-nutritious foods, and get plenty of rest. In time, the fitness will come.