I feel trapped

Hello guys ! You’ll soon understand why I’m looking for your help and advice ;)
I’m 21 and I’ve been in a relationship for more than 5 months. We’re still together now.
This guy is different from anybody I’ve ever met before. He’s calm, he can be very tender, he’s patient, he continously reminds me of how much he’s fond of me.
I’m discovering a new side of my personality thanks to this relationship.
Problem is, I don’t like it.
What I’m discovering is not sweetness or deep feelings.
I’m discovering some sort of cruelty, and the thirst to feel free again.
We’ve been seeing each other almost every day during these months, we’ve already been on holiday together, but the more we get to know each other, the more I feel like an alien in this couple, I have few feelings for him, and I’m starting to get bored.
I never thought I’d ever have to deal with boredom with a tender guy. I thought everything would get along perfectly, understanding each others’ needs and loving each other of a very deep sentiment.
I hope I won’t sound indelicate saying, that luckily there’s still quite a lot of sex spark, when it’s not programmed I really enjoy making love to him, but still, when I’m alone I don’t really look forward to spending time with him.
I tried to leave him once, told him (as kindly as possible) that I’d started to feel the urge for freedom, that I felt a bit suffocated, that quite often I wanted to be single again. I did blame myself for these cruel thoughts of course. The way he responded to my words was disarming. I really felt I couldn’t leave him anymore : he told me he was so anxious, that the night before I spoke to him he hadn’t slept and had smoked 30 cigarettes. As we talked, he was trembling and on the point of crying.
I really did feel like a worm in that circumstance, so I told him I was sorry. That I would stay with him and that those bad feelings would pass, that he was a caring young man and a beautiful person.
At first, although my purposes were cruel, I thought he’d understood what I’d been talking about. He told me he was aware of my sense of suffocation. So at first I thought we were back to the idylliac beginning.
He says « I love you » many, many times.
It used to flatter me.
That’s what all women look for: explicit appreciation.
But after our discussion, he says it really (and I mean really) often, as though his purpose were to see if I reply or not. He tells me about his disappointment when I don’t feel like saying many praises and many « I love you too » back to him. I do understand his concerns. They’re the reason he continously wants explicit confirmation of my interest for him.
But I’m starting to suffer too. I’m not truly glad to see him, I feel obliged by my conscience.
My mind tries to convince my gutt that he’s intelligent, caring and charming. That he’s the man for me. Still, it does happen I feel a sense of reject for him. I feel terrible.
I never thought love should have anything to do with pity, let alone when you’re not in a married couple.
Maybe the deepest and most truthful reason of why I can’t find the courage to leave him, is I’m scared I’ll start feeling lonely again. I’ve suffered loneliness quite a lot in the past. It’s a dark sensation, it can be horrible and can ruin the way you perceive yourself and your friendships. Friends simply aren’t enough at times.
But I do think coherence of thought and action should take the lead on any fear. I’d like to be coherent with him, and stop lying on my feelings.
Deep inside I know I’m acting like an asshole, I really would like to avoid any suffering to him, and so here I am. Trapped.
What is your opinion ?