Plan to get back in shape

I've really packed on a too much fat these past 6 months and have totally been neglecting my exercise routine.
What triggered the unhealthy eating and lazing about too much?
I am 99% sure that it is a particular medication, a "mood stabilizer" that I started taking again last year.
I was taken off this particular medication about 10 years ago after I had ballooned up to 300 pounds and I proceeded to get my weight down to a much healthier 235 over the span of 2 years.
I stayed at or around that weight until I suffered a rare bout of mania in early 2019 that was triggered by a course of corticosteroids that I was given to treat an upper respiratory infection. That is according to my psychiatrist who helped see me through the upset.
Anyway, about the weight and exercise:
My plan is to cut back on sweets and use portion control to eat smaller but well balanced meals. Nothing radical. Just common sense.
As for the exercise, I have a great wind resistance air exercise bike that I used to love to use 4-5 times a week. It is sitting here in my family room beckoning me to "get back in the saddle again".
I am still on this particular medication that seems to cause this reaction in me but I am not going to use that as an excuse to not make an effort to get this back under control.
My psy-doc is willing to work with me with the meds but not until things have settled down for a while otherwise.
I'm not going to force myself to do anything as far as diet or exercise go.
I am putting it out there though that I am going to make an effort to get back to healthier eating habits and ride the bike 4-5 times a week.
Let's see how things go until the end of the year.