If a man says he has reservations about whether he is IN love with you. Says I love you What does it mean?

Been with this man for a year,(known him over 3 years) we have been thru a lot...stress etc. But things are better. At times I feel so blissfully happy and others not so much. We fight but get thru it fast. I explain to him how ecstatically happy I am at times, and others are so opposite. He said to me he is in Love with me with reservations. What does that mean. We are engaged for 7 months now....