Questions: Relationships

When we just started dating my boyfriend was very loving, unlike any other guy I have dated before. He always made time to text me during the day even though we’re both busy working, called me straight after work and we could chat for hours, sent me flowers, always compliment me and tell me daily that he loves me, once he even flew to another country to see me and take out for dinner also he insisted and paid for the tickets just for me to go and see him and it was like this for a year but now as we are dating for nearly 2 years I just feel how everything has changed. He texts me just good morning and it’s every day the same like he does it because he has to not because he wants to. No more texts unless i text first and he gives a dry answer or he needs something, in the evening he is usually busy or in the best case calls me for 15-30 min and then says that he still has things to do and has to go. Even when we talk for longer I can say that he’s not really listening and just starts doing something around with me on the phone. He stopped saying that he loves me unless I say so he can answer with I love you too. When I ask him if everything is ok and if he wants to be with me because I feel that he got a bit cold he always says yes, that I am overthinking and should stop asking silly questions. Is it time to get worried or am I actually just overthinking and it is normal that after some time things change this way?