Relationship in trouble, issues with infidelity, help!

May I suggest that these conversations that he is having with this girl are already inappropriate?

And, not for the reason you may think. Sure, men and women can "hook up" and still be friends with this person, while in a current healthy relationship. This is the part that is lacking...your boyfriend is not in a current healthy relationship, as he is not actively caring about your feelings or concerns.

I know this is difficult, but it really does not sound like he is interested in an exclusive romantic relationship with you, by his actions. He may WANT to want an exclusive relationship with you, but his choosing to actively pursue a past intimate partner, while beginning a new relationship with another woman (you), is not indicative of his being ready to initiate a strong foundation to a new healthy and happy relationship.

If you are wanting (and deserving) of a boyfriend who is "into you", and not also needing outside attention from other girls, all you can do is control your own behavior and choices. You can talk with your boyfriend about your being uncomfortable with him talking with his recent "ex's (for lack of a better term). If he tries to back you into a corner by asking how you know, or denying it, or making you feel like a control freak (or any other number of manipulation tactics), you can simply say that you are sharing your feelings with him, he does not need to agree, but he needs to respect them if he would like to continue this relationship, and if he would like a long-term exclusive relationship with you, that you felt he needed to know your feelings. (Your feelings are not "out there" or abnormal, and are a very healthy boundary. An unreasonable boundary would be telling him he's "not allowed to speak with any girl", but most reasonable men and women would agree that they would feel uncomfortable with their bf/gf talking with/pursuing/getting drunk around a very recent past hook-up. This is just normal. He may not be interested and want both outside-girl-attention and you as a girlfriend...he may not be ready for an exclusive relationship, which is OK and does not make him "bad"...but he does need to mature and speak his truth, be authentic and honest with you and himself). The ball is in his court, and he has the choice to be mature and talk with you about what he wants (exclusive relationship with you and complete freedom to talk with ex's, an open relationship where he can date other women, etc.). Then, you have the responsibility to decide what is OK with you in a relationship. There has to be mutual communication, trust, honesty and healthy boundaries to make a relationship work. It really is about choices, and what type of relationship you both want. Sneaking around, ignoring another person's concerns, having the energy to talk with/pursue recent past hook-ups...these are not signs of a healthy relationship...and you can choose what is best for you.

Lastly, I think it's important that he knows this is not a request, favor, expectation or controlling behavior from you. You are not asking him to change his behavior; that is his choice. What you are simply doing is being honest and open with him, letting him know your feelings and concerns, and he then has a choice with what to do with that information. He can ignore it and continue sneaking, he can ignore it and make you feel bad about your feelings, he can listen and talk with you about your feelings & what his concerns are, he can listen to you & respectfully disagree and say he still does want to talk with X girl...there are many different scenarios, and you can then make your choice with that information. It is important to not push him into a corner with expectations, rules, guilt, etc...he may continue to sneak more effectively...but give him space to openly share his thoughts, disagreements, concerns, feelings, wants...and you & he may or may not be on the same page in the relationship at this time. That is really what you are trying to find out...not trying to change or manipulate the other person, but learning about each other's desires and wants at this moment in time. Then, you both have the information you need about the other one to make an informed decision to stay with each other or to leave on good, healthy and mature terms. (Does this make sense, as he has a choice too...if he wants to talk with this past hookup, and has a girlfriend that is uncomfortable with this chosen behavior...he needs to make a choice about what he wants to do without trying to change you...he can only control himself, and hopefully he has the integrity to be honest with you about what he plans to do).

I hope this helps!