Yes. You’re overreacting. 😕 If your goal is to make this relationship work, and you’ve been together for three years, with the last one of those three years long-distance, you have to focus on that goal. 😉 You’re not with him to date him while this is long distance, and there is going to be competition. That’s just a fact of life. It may be difficult, but that’s part of the challenge of long distance relationships. You have to give people in these long distance relationships a lot more freedom if you want them to work — and that goes both ways. He has to give you more freedom, as you have to give him the same.
So, instead of blaming him for accepting gifts and possibly dating this other woman, why not accept the reality of a year or more of distance, and compete for him! 😎 If she gave him a birthday present that indicates she’s interested in him, you have to give him a present that’s more meaningful. 🙂 Be the girlfriend he really wants to be with — above all others. You’re not engaged, but if, as you said, he wants to marry you in May of 2017, then why not celebrate the commitment that the two of you have, instead of creating arguments. Yes — you’re right. This other woman likes him, but that doesn’t mean you can’t win him! But, because of the distance, you have to avoid arguing with him, and if you can’t, reconsider the long-distance relationship. These are very difficult to sustain for many people, and it’s understandable that you’re trying to apply “in town rules” to an out of town relationship. Ease up, hang back, and be that girlfriend that gets the guy.