I know many people who ride alone, and I am one of them.
If I were to wait for someone to be with me to ride, I'd never beable to ride. Don't get me wrong, it is great to beable to ride with another for company and companionship and conversation, but most of the time, I wouldn't beable to ride if I had to ride with another.
Back at the barn I used to be a Working Student at, there are a ginormous amount of trails to ride on, because it was the barn of Fox Hunters. I would go out for hours on my own and ride, that is how I learnt the trails.
I know those trails like the back of my hand now - but before I left, the BM would be notified, and while grooming and tacking up, others who were tacking up as well to work in the arena would be notified.
There is a large white board as well hanging near the tack room, and when people would go out and ride, including myself, would write on the board. Time leaving, name, place, date, time planing on getting back. Then, if the BM or others would see that the rider was not back at the time marked, they would get on 4 wheelers and head out on the trails to find the rider to ensure all was ok.
Another thing I do, is carry a cell phone with me. My Hubby and I luckily have the walkie talkie options on our phones, so if something were to happen, I could 2 way him.
I also have nasty allergies. I am allergic to dust and anything that holds it - like hay. I end up having allergy enduced athsma and due to that, I have to carry my epi pen with me and an inhaler. I wear a fanny pack. So you could carry your cell phone in something like that.
You can also get a cell phone holder, these are awesome. I have one of these! Dover Saddlery - Search Results for cellphone holder
You can put it around your arm, or, do as I do - which is wrap it around my tall boot, near the top.
Anything can happen at any given time - with or without others being around you while you ride. We are on very powerful animals with minds of their own, so expect the unexpected.
Now, if you are this scared to ride alone, then listen to your gut - because it never steers you wrong. I am not here to tell you that you are crazy, or your feelings are nonsence, because that is not what I think.
I think this is a work in progress. I think starting lessons is a great idea, this way you can start to buid your confidence in the saddle which will give you the essential tools you need to be stronger physcially and mentally while riding.
There are Coaches who will come to your place as well. My Coach does, it is a little more expensive because the cost of her drive is added to the lesson fee - but that's something I am willing to spend because she has all the quallifications I want in a Coach - and because I do not have a Truck nor a Trailer to haul. So it's either that or ride under a Hunter/Jumper, which isn't my cup of tea.
I wish I could throw out more ideas for you -