Okay so your reply is a little confusing I'm not sure where to start.
First of all lets start off with PrEP. This is something you take when you are HIV negative to prevent you from catching HIV and it should not be taken if you are HIV positive. If you take PrEP when you are HIV positive it's not enough to completely suppress the infection and there's a strong chance that the HIV inside you will develop immunity/resistance to the drugs in PrEP. Obviously this is a very bad thing.
When you first become infected with HIV your body goes through a process called sero conversion. This is not instant and can take up to several weeks. During this time the HIV virus starts replicating inside of you and causes what's known as an the initial acute HIV infection. Once the numbers of the virus reach a certain level it triggers your body to defend itself with a big immune response. During this time the copies of HIV in your blood are very high, this is when your body develops its own antibodies against HIV and you can become very sick. I say, can become very sick, because how sick varies greatly from person to person. One of my friends almost died and was in hospital for 6 weeks when he was first infected. Other people have no significant symptoms but it's common to have flu/cold-like symptoms and just feel under the weather.
Once the body has fought against HIV in the acute stage it has won that first battle and developed its own antibodies against the virus. This is also when you will now test positive for HIV with most standard testing. You start to feel better and the copies of HIV in your blood falls to very low levels. Low but not undetectable. As time goes on the copies/ml, in your blood, starts to rise and as it rises the number of white blood cells, known as T-cells, start to decrease. As the amount of HIV gets higher and higher you end up with fewer T-cells and when the number of T-cells gets too low your immune system starts to fail and you are said to have AIDS.
As far as I am aware you do not normally become undetectable unless you are on medication. After the acute phase the amount of virus in your system will be low, but not undetectable low.
There is one caveat to this though and that is some rare people are naturally resistant to HIV and end up undetectable without medication. This is very uncommon and if it were the case with you I would have thought the doctors, handling your long term treatment, would have told you this. It's important for you to know, both in terms of what your long term treatment plan might look like, but also so you know what risk you pose to other people. Clearly they didn't do a good job with you as you've been left confused by what's going on.
If you are indeed one of these rare individuals then consider yourself lucky! It doesn't change anything with regards to long term disease management though. You will need to have regular 3-6 month blood tests to monitor your condition. Usually HIV positive people are monitored whilst being on medication. This is to check that the medication is still working (keeping them undetectable) and to make sure the medication isn't destroying their kidneys or, in some instances, their liver.
You will need to be monitored to make sure that you're still controlling the virus levels yourself, and remaining undetectable, but other than that your kidneys and liver get a free ride.
Is it possible the doctors talked to you about this but you missed some of the points because they were bombarding you with so much information? If I were you I would want them to give you clarification, just to make sure you really are controlling the virus naturally, in case the doctor you saw was mistaken or a bit of a quack.
How many times have you had your viral load tested?