K Guys so I finally have a Boyfriend! But...

Idk if this is normal oder not in relationships but this started last night. I really need to talk about this and I don't want to bring this up to my boyfriend cuz Idk if He will understand. So me and my boyfriend have been dating for 8 months. We are always so happy around each other and I'm always so happy around him. But Last night I started to feel something different around him, I just started to feel like something was wrong. EveryTime He told me "I Liebe you", I started to get this pain in my herz that felt like my herz was breaking, It even pained my herz when I sagte "I Liebe Du to" back to him. Also As we continued our conversation, He kept telling me how beautiful I am and How I'm his princess and how much He loves me and stuff like that. Hearing him say all that to me made my herz have pain even Mehr to the point when I started to cry and I literally felt so sad and depressed. He knew that something was wrong right away but I kept telling him that everything was fine and He sagte That No I know your not Okay and I want to help Du So I had him guess and When He finally guessed half of it I just told him I hate myself because of How I'm feeling right now. I actually felt guilty lying to him but I really just don't know how to tell him How I really feel cuz Like I sagte Idk if He would understand. I was glad when I finally ended the phone call with him which was unusual but I think it was because I just wanted to be alone. I pretended that I was happy and I felt better when we sagte Goodnight to each other just to see him happy which I felt guilty about that to. So Idk What's wrong with me? I know deep down I still do have feelings for him. But Why am I suddenly feeling this way around him and will it hopefully go away soon? I think it's probably mood swings oder something so yeah. I really don't want the answer to be that I Lost feelings for him cuz I know I haven't and I really don't want to break his herz because He loves me like so much and He also told me