I need help please...

With all you are going through I would attribute this to stress.
However..If you have had other episodes that concern you it might be a good idea to see your doctor. Please tell the doctor what else is going on in your life as well. That not only effects your Mental Health it can effect you physically.
I bet there are many times you have driven home from the store, work and been on "auto pilot" and if someone were to ask you what color house is on the corner of Main and Pine you would not know even though you pass there almost every day. You would not know if the light was red or green, you just stop, it is an unconscious response. So I would not worry much about not recalling how you got home after a stressful day at the hospital.
You do need a break and I hope you have help if not it might be time to start looking. Might also be time to reevaluate your parents living at home. If they are living in their home they will be needing help so Assisted Living is an option but Memory Care might be better. If they are living with you they will both need more help sooner than later and can you handle that?
You are your first priority then your family.

I agree that this is completely caused by stress.

Can you take a break? Please get someone in the family to step in (or hire a caregiver and give yourself a breather.

If you can get away for a week, you will be better able to take on the battles when you return. You don’t want to end up in the hospital.

You may have experienced Trans Global Amnesia and its caused by stress. I had a coworker who couldn't remember how she got to work. She was told she probably would never remember that time. Her stress was from worrying about her only child who was helping to fight a large forest fire in another state. My Mom suffered it from a head injury from a week earlier. You may never experience it again.

LLacey, do you have a primary care doctor? If so, call her/him and describe what has happened.

If you dont have a PCP, I would get myself to Urgent Care today or tomorrow and have yourself checked out thoroughly. Not for dementia, but for an acute condition that may have caused you to blank out temporarily.

Stress and lack of sleep can wreak havoc on your memory, reasoning, emotions etc. It can cause chemical and hormonal imbalances as well. Before paying for a bunch of tests or totally freaking out, maybe take a moment to assess yourself.
Am I sleeping enough?
When was the last time I did something that allowed me to stop worrying about those I'm caring for?
Am I eating well?
I would suggest a weekend at a local hotel with the phone turned off before going into all the medical testing. That way you can rule our sleep deprivation and stress as the cause.
You might also consider that at 49, you could be in the early stages of menopause which can cause mental confusion and hormonal changes too and if you do go for medical testing maybe start with a gynecologist visit.

Do you have high blood pressure? The blackout sounds more like a TIA or mini-stroke than early onset ALZ to me. The memory blackouts were the first indications of what would become my father's vascular dementia.

But YES, you should see a doctor ASAP! If it is a TIA, sometimes those precede a major stroke by only days.