Hi Sogno,
It doesn't have to be a bad experience. Clearly there will be changes happening in the body, such as changes to hormone levels etc. and these can have an effect on the way the body physically feels as well as the way the brain functions. For example, seratonin is a hormone that is important for the correct functioning of the brain and when levels of seratonin fall this is a common cause of depression. Seratonin is often referred to as the "happy hormone"
However, these are the things that are happening in the mind and the body and clearly you can observe these things happening.... but... if you are observing them, you can't be them. You are actually the observer and you can choose to distance yourself from the thoughts and activities of the mind or the pains and discomfort of the body and recognise that nothing, absolutely nothing, can stop you from being You, the observer.
Saying that, you do need to observe what is going on with the body and mind, and act in accordance with the needs of them. So, if you are observing pain in the body, you can stay detached from the pain, but take action to deal with the cause. Likewise with the mind, if you observe that it is not favourable i.e. it is becoming depressed or upset, you can observe this from outside and objectively look at what the causes are and what action can be done to help resolve it. These may involve seeing your doctor, but you can at least start to recognise that You are not sick, and You are not depressed, these are things of the body and mind that can be overcome with patience and postive action.
Keep us posted how you get on.
Hugs
Giles