Don't ride a road racing bike then, dummy.
Get something more durable and relaxed like a touring, gravel or hybrid bike. When you're heavy you don't even need to care about weight so you can manage on a cheap steel POS and a cruiser saddle for your fat ass.
Go at your own pace and in a year or two you'll have a much better time. The most important thing is doing *something* so your metabolism stops hoarding fat and your blood sugar gets spent on something other than making you insulin resistant.