Do not worry. You will always be you.
Instead of thinking "What if?", think "So what?" as the diagnosis is a tool used to help make life easier through the tougher bits.
So do not worry as you can't add a single hour to the day by worrying. I hope this helps?
Whatever it will be, it will be!
Also, just to add some information. Autism highs and lows can be very up and down and spiky. In other words, an autistic person who has highs and lows can go through several a day!
Bipolar highs and lows are caused by a chemical imbalance in the brain which takes a while to turn from a high to a low and back (Typically a 4 day cycle between a high and a low or a low and a high I have heard). The lows and highs are very extreme. Is important for a correct diagnosis as those diagnosed wrongly with bipolar when it is autism can have double trouble to deal with as bipolar medication can actually cause bipolar symptoms in someone without bipolar, as bipolar medication is trial and error to try and restore the brains chemistry by adding the chemicals via medication. The GREAT news with bipolar is that with the correct dosage, the patient can go on to live a normal life. They will need checking now and then that the medication adjustment is right, but it is treatable.
Autism is NOT in itself treatable, but certain associated conditions caused by the autism which some autistic people can get can be treatable.
I hope this helps? And finally, Do not worry!