Neither 「そうですか、ありがとう」nor 「ありがとう」is appropriate, because they lack the sense of humility required in Japanese when receiving a compliment.
とんでもない should be said, regardless of how hard you may have worked to get it or how proud you are of it.
Your boyfriend said it's stupid because it shows ignorance of Japanese propriety and common sense (provided that it is said by a Japanese native speaker, of course--tolerated when said by foreigners).
When you give a gift (that you probably paid dearly for) to a person, you say: つまらない物ですが・・・ (it's something worthless)
Note: This is said most commonly when giving gifts as protocol (such as New Year or summer-season "chugen" gifts) and does not apply to true person-to-person gifts from the heart (such as birthday gifts).
HTH!