Your question is important and it is highly obliging. First of all thing that should be understood is that HIV and other blood disease are contracted when two different kind of blood compositions meet. This can happen if you get in touch with the infected person through the blood. If you are having any open wound and somehow that wound comes in contact with the blood of the person who has this disease then there are chances of you to contact blood transmitted diseases.
If you are having g sex with the infected person then you should use protection because this only saves you from becoming a secondary carrier of this disease. You said that you had oral sex then it does not really mean that you have contracted it because this does not spread when male penis comes in contact with a woman’s saliva until she is having her saliva contaminated by little droplets of blood that may be present if she is having ulcers or things similar to these in her mouth. If you have unprotected sex that involves the mating of penis and vagina then there are possibilities of anything like this happening to a person. Even if the penis comes in contact with the anal cavity during anal sex then also there are positive possibilities of it.
To tell you about a venereal disease, well it is a disease that is caused due to any type of sexual contact and development of any kind of micro organisms on the genitals. A venereal disease if contracted must be dealt with immediate urgency. Have a nice day.