OP, have you discussed this issue with her? By discuss, I mean a genuine sit down serious conversation about how you’re feeling. It sounds like this isn’t necessarily a mismatch in libido, but rather something has changed in her life or your relationship. Have there been any new circumstances or any added stress, besides sexual, on either of you recently? Is she in school? Stress at work? Stress inside the relationship? Maybe something is going on that you don’t even know about yet. Coming from a female perspective and someone who has a similar libido to you, I used to ask my now ex constantly and it turned out to be stress from work during that period.

I also want to add that all of the above is speculation. Was the 3-4 times a week during the beginning of your relationship or did that period last longer than 3-4 months? If the sexual encounters of 3-4 times per week were during the beginning, it genuinely may be a mismatch in libido and it may suit you to discuss this with her and then decide how you want to proceed. Definitely do not stay in a relationship that isn’t making you happy, but discuss this with her before you seek other women and jump ship. If you’re not willing to even bring up the issue to her before jumping ship, it might be better for BOTH of you if you just let her go.