In my experience, many people with medical conditions are able to obtain travel insurance through a specialist provider. You will be assessed on an individual basis, which will take into account a number of things like your health, age, where you are travelling to and how long you are going away for.
If you find it difficult to talk about your condition, you might want to consider asking a friend or relative to be there while you make the call or they could do it for you as long as they have all the relevant information to hand.
It is also useful to know that most travel insurance companies use a medical screening process to determine if they can cover you.