It may be a metaphor for your boyfriend to say that you are like a lamb, which means that he thinks you are gentle and lovely and needs care and protection. This statement is usually not derogatory, but implies spoil and love.

Of course, everyone's expression and mentality are different. If you are confused about your boyfriend's real intention, you can directly ask him why he describes you like this, so as to better understand his thoughts and feelings. In communication, you can express your thoughts and feelings and ask his views and attitudes, which can deepen mutual understanding and trust.