Boyfriend of 8 years, detachment

have been on Citalopram for just over a year. I feel completely devoid of emotion for my boyfriend of nearly eight years. To see the hurt in his eyes when I tell him I don’t love him just breaks my heart. I feel tremendous guilt every day, and often think it would be easier to leave, if only to let him get on with his life, and to stop this guilt I feel. I have no idea if this detachment I feel is because I really don’t love him, or if its a symptom of this depression, or a side effect of the Citalopram. Every day just seems a nightmare.