Yes, but that is not always a disaster.
This is the lifestyle of love:
It starts out as some attraction. The stronger the attraction is, the more it is based on our repressed pain and our fantasy about the other person, so the more quickly it will die out and the more it will hurt.
Psychologists warn us that the stronger the chemistry is at first, the worse the relationship will be later on.
That the fantasy never lasts, and the longest it can last is up to a few years after marrying. And when it dies out and we start to see the other person clearly. But the fantasy may die out hours after we meet .. When it does die out, usually the interest does too. Because all we liked was our "high" over the other person and without the "high" they no longer interest us.
Also that people who ARE emotionally mature to make it last, the men take about 12 months of steady dating before they know they are serious about her .. .and the women take only 6 months before they know (note the discrepancy here ... the woman has to be happy enough on her own, to wait and see IF the man decides to become serious too).
And that we are never happier in a long-term relationship, than we were happy when we were previously alone.
As for wondering what is happening, YOU have to communicate with him. If you cannot do this, then the relationship is going to fall apart sooner or later. TALK to him.
Relationships that last tend to build slowly and mutually .. not at all obsessive. After about 2-3 years of dating, up to as long as 2-3 years of marriage, they get along. And then the problems start. All relationships end up having problems, because no one is perfect. But couples who have a chance pf making it work will stick it out and work together.
So this is followed by a long phase of sometimes getting along, sometimes having conflict .. sometimes loving each other, sometimes not even liking each other.
Somewhere around Year 12 to 15 of the marriage, the couple burns out. They become alienated. But if they hate change they stay together.
And then - for 12.5% of couples - something happens around Year 20. They have both cooled down from the heat of burn-out and one day one of them looks at the other and remembers why they fell in love .. and they decide to NOT let the problems bother them anymore. They decide that having the person is worth having the problems too. And love blooms again except this time there is no passion or obsession .. no fireworks ... just soul soothing trust, nurturing ... a haven for both of them.
As for astrology, Sagittarius is ONLY his Sun sign. And all it indicates is how he relates to himself in an attempt to feel whole inside. It is NOT his emotional nature (that is shown by Moon), nor his relating styles (Venus), nor how he is about romantic love (5th House).
If you want to use astrology, use it.
And never excuse poor behavior saying "I expect it because of his Sun sign). YOU set the standards for what you get out of a relationship, and if you cannot get what you want, then you should not be in that relationship.
And if you are afraid to make things awkward .. ALL relationships become awkward. Don't let fear make you a passive victim.