hello and thanks for your question. I would like to start by saying you have done well to acknowledge that this behaviour is not what would be considered acceptable in a relationship and you have sought assistance. You don't actually mention that this fetish is sexually link, although you say that it involves 'no assault', but you have mentioned online pornography and I therefore have made the link between the two. You ask for a view on this and I would like to give you my view.
Many people have fetishes and in some ways, there is nothing wrong with them, as long as they stay as harmless fetishes. However, it is highly possible that your expectations from a relationship would be shaped by your fetishes (you have already identified that the two don't mix and you think it would be best to give up before finding a girlfriend) and they would therefore stop you from having a healthy relationship or your relationship becomes tarnish by them. Fetishes are also likely to escalate, which you have experienced by your explanation that they are becoming darker. You ask why they are becoming darker -this is because when we are exposed to something more often, we become more used to it and need more of it or stronger measures of it, to get the same kick. It's the same with drugs, alcohol and other addictions. A person needs one more drink, or one more hit, to el the same as they did
yesterday. Its the same with this fetish which may start off free from assault, but may slide into a little anger, more anger and then assault and violence, to get the same kick as before. The issue about you not wanting to be doing this by the time you have a girlfriend in insightful, for I suspect you are thinking that your girlfriend may not wish you to browse it. I would be more concerned that you would be wanting to act out your fetishes, because at some stage, looking at them is no long enough. I would also question that you would choose a different type of girlfriend if you were looking at these images or not at the time, as you may subconsciously be looking for someone who fits them, rather than someone who you truly like. I would really try to give them up before you even start looking for a girlfriend or this could become more of an issue than you haves anticipated.
Like I said before, you have made he first major step by recognising your issue and asking for help. search the internet for a local sexual therapist and make an appointment. If you feel that this may have come from an incident related to the past, seek for an EMDR therapist, that's stands for eye movement desensitisation and reprocessing, which can help you to identify beliefs and images from the past and to let them go so they no long affect your life. A therapist who specializes in sexual stuff won't be embarrassed or upset by what you tell them, as they have heard similar stuff before and have studied how to help you, so please try not to be embarrassed about it. I do hope this helps you and I wish you well. Sort it now before it gets out of control. Best Wishes, Sarah