Let me tell you a story. Many years ago, I used to have a friend called Stacy who was in a rush to start having a sexual relationship with, come to think of it now, every man whom she strated to date. One day, she did not come into work and, later that day, phoned me for a chat, which I remember like it was yesterday. Half way through our chat she asked, "aren't you going to ask why I didnt come into work today?", so I did, and she explained that she'd spent the previous two nights in bed, not sleeping, because she had developed all these warts on her lady area, and that they were that painful, that every time she moved, they would open, and that, due to them being so painful, every time she needed to pee, she would have to do so in a bath full of water, so to dilute the urine immediately, before it could get to these open wart lesions. She told me that she'd gone to the clinic and was diagnosed with genital herpes and was informed, as Claire says, that these are something that you cannot ever get rid of. So, in my friend's words, which still resound in my head, she said "Now, if I ever want to have unprotected sex again, I am going to have to say to my partner: This is what I have, and this is what you have to be willing to carry." I felt so bad for her.
What am I trying to say? Sexually transmitted, incurable, infections are very real. As Claire has already explained, even using a condom, does not protect you from some of these, due to the locations in which they may appear, and their presence on the body irrespective of whether you are even aroused, or penetrating someone, or not. The fear which the title of this thread speaks of is, in reality, not really a fear, it is due caution. Finding the 'right', and suitable, and clean, person is a long, but necessary, process for many, but when you find them (and to know if they are 'right' you will have to spend time getting to know them), for however long that partnership may last, you will want to be spending many hours of intimacy with them, and what kind of additional problem are you going to have, then, when, because you were wanting to rush into sex before, you now have co-habitants living on your penis wanting to meet your partner, because your doctor has said they are above even his expertese?
So, I think you need to throw away the word "fear", in your mind, insofar as it is a debilitating condition, and change it for the words "sensible and wholesome and proud" about the way in which you see yourself in this current situation. Devote the rest of the energy that you are devoting to all this, to healthy eating and life-style in which you can perpetuate these values, alongside your self-development. Dicard of giving rulership to the low level, base, primal, urges, that you report. Note, the latter factors are healthy in their own way, but they have a place and, due to the society in which you live, their place has to be not in the forefront of your mind, but in a side-pocket that you dip into when you choose. I don't know a great deal about hormones, but the older I become the more I realise that there is something fundamentally challenging about having a sea of testosterone flowing through a body, as many males experience. If it helps you at all, know that as long as sex is something which you crave, it is also something that those who give it to you can control you with. It is an important, but wonderful and liberating, choice. You have to find your way to it. What an interesting subject.