In the beginning, he did little things to prove his love for you every day. He was attentive, planned romantic dates, and he wanted to spend every minute of his free time with you.
That all is gone now. You feel lonely most of the time because you barely spend any time together. There are no more romantic surprises and you just feel that the spark is fading away.
You are probably right and you should at least talk to him about it and see what’s going on. If your feelings are not reciprocated, you shouldn’t waste a minute more of your time on him.
A lot of things can be fixed but when there are no feelings from both sides, the relationship is doomed.