Doglover,
I am going to take a completely different angle than anyone else on this thread. Because I noticed a lot in your original post that has not been addressed by myself or others yet.
If you go to your original post and read it over, you may see that you went after Lukas, made the first move. The relationship began and developed through your actions.
You initiated a relationship with someone who seemed reluctant, or not on the same page as you, or maybe to naive to know what a girl wants. You were the first to touch him and want him to touch you. Touching his leg, giving him a hint in order to get him to hold your hand (which he ignored), trying to put your head on his shoulder (which he ignored), and hinting more about about having cold hands.
You did not want to set times to meet him because you were afraid he would not take that seriously and be there. Sad to say, you sensed that what you felt was not mutual and you would need to be careful about how you proceeded. (Hey, I have been there myself and know the feeling.) So you went to where you thought he would be and met up with him, running into him. I am not quite sure when this became an actual dating relationship or if it did. By dating I mean he says, “I would like to take you out to dinner, what night are you free?” And he picks you up, drives you, has the restaurant or activity planned. You need do very little because he wants to be with you and arranges to. I am unclear if that happened.
After being in a relationship, you were the first to say I love you and you asked him if he loved you. He said he did. Later, you saw him looking at a photo of a woman in lingerie.
I have been thinking of this course of events and what it means since I read your OP.
I hope this does not offend or hurt you. Could it be that seeing him look at that picture made you feel insecure because along the way of getting to know him you sensed that you had more feelings for him, that you wanted closeness when he initially showed no interest in being physically close to you? Could it be that you are focused on the photo and the “phemonon” of what it means because it hurts that you had to wait for him to show interest in you, and this is the reason you want to remain single, presumably for the rest of your life.
Of course, being “single” - never marrying, never have sex, never having a boyfriend - is safe. That way you don’t put yourself out there again to get hurt by someone you liked, loved, who didn’t have the same feelings as you had. Someone who ignored you when you said that your hands were cold, who pulled your sleeves over your hands when what you wanted was his had in yours, someone who did hold you hand finally, after more hints, and someone who willingly gives his eyes and attention to a woman who seems sexier.
Well, if you want to give up future chances for a true two way relationship, mature love, marriage becausd this child did this thing you don’t understand, I feel sorry for you and wish you would take another look at what you are thinking and what this relationship lacked that you can have in the future. I really seriously care or I would not be up until 4 a.m. California time writing this.
Take a break from guys, from thinking these serious thoughts, decide not to date for awhile, but don’t give up totally. Actually, I remember in my twenties whenever any of my friends would take a break, the right guy would come along out of the blue.
Just have fun and forget what guys want, what other women you know think is natural, etc. Girls just want to have fun, right?

Don’t make any pledges to yourself. Leave your heart open.
I leave this thread with those thoughts and wish you the best.:hug1::