It really isn't necessary at such an early age unless from a safety aspect. Swimming should be about fun, first and foremost! We live in a hot climate, have a pool and our small island is surrounded by water so from my point of view, it was essential that we got DS1 swimming, or at least not drowning from an early age.
But I still didn't do actual kiddie lessons with him until he was 2 years, prior to that we splashed around, went under water and just got him comfortable.
He's 3 at the end of next month and can now swim unaided (no floats or armbands) and can dive and collect toys from the bottom of the pool, but this is far more to do with the amount of time he's exposed to the water than just the lessons. It is now instinctive for him to jump in and automatically swim to the side and that was the only thing I wanted to accomplish.
I was a very good swimmer as a child, but we didn't start swimming lessons until we were about 5 years.
DS1 won't start learning actual strokes for another year as he doesn't have the attention span. DS2 is 5 months and I just take him in the pool in his floaty. He loves to kick his little legs but the same comfort with water can be achieved at an early age with taking them in the shower and letting the water run over their face and from splashing at bath time.
Congratulations on your weight loss, that's incredible!