But whether or not it's a problem, all comes down to balance. Is there a natural give and take - sometimes you doing the caring, and sometimes you're cared for.
Co-dependence is a problem of the above relationship dance being stuck - where the emotional traffic is all one way. It may have started off that way, or it may have developed over time, but perhaps what your friends are concerned about is whether you're able to rely on your partner to care for you, to put you first, when needed.
To put it another way, can you talk openly about your feelings and troubles, and feel that he is there to listen, and support you - at least the best way he knows how.
In its most extreme forms, co-dependency includes abusive relationships, or relationships that support or tolerate one person's bad behaviour, like addictions for example.
You've already said he's not abusive, and I'm very pleased to hear that, but the ultimate test of your friends' concerns is whether you can talk to him about any concerns you have.
Other people are welcome to their opinions of course, and when we feel our friends are in unsafe situations we should absolutely raise it with them, but it's also true you're the ultimate judge of whether you're happy, and whether your relationship works for you.
Within common sense boundaries, we get to have whatever relationship we want, even if that wouldn't suit someone else. It's also true over the course of a long-term, committed relationship that the tide of giving and receiving can take longer cycles - again really the only test is whether you can openly and respectfully talk about it with each other.
Not whether they're comfortable talking about it, but if they're willing to talk about it. Sometimes we find ourselves off-balance in relationships because without the ability to talk about it, we just set sail and accept the course we're on, without knowing how to alter our course intentionally.
Talking about it is always the course correction.