While I cannot definitively say whether your ex was cheating on you during your relationship, her behavior of continuing to sleep with you while being in new serious relationships is certainly a cause for concern and may indicate potential infidelity.
There are a few possibilities to consider:
Cheating during your relationship: It's possible that she was involved in some form of cheating during your relationship with her, which may have contributed to its end.
Emotional attachment: Even if she wasn't physically cheating during your relationship, her continued involvement with you after starting new relationships suggests a lingering emotional attachment or unresolved feelings.
Pattern of behavior: The fact that this has happened with her last two boyfriends indicates a recurring pattern of behavior. It's essential to consider whether this is a pattern of using others for emotional or physical comfort while in a committed relationship.
Commitment issues: It's possible that she has difficulty fully committing to a new partner and seeks comfort from familiar sources, such as reconnecting with exes.
Regardless of her reasons, it's crucial to assess whether this situation is healthy for you and if it aligns with your values and expectations in relationships. Sleeping with someone who is already in a committed relationship can lead to complicated emotional dynamics and potential harm to all parties involved.
If you are uncomfortable with the situation or feel that it's not appropriate given her new relationships, it may be best to set clear boundaries and distance yourself from this dynamic. It's also essential to have open and honest communication if you decide to address the issue with her or seek closure.
Remember that everyone's behavior is influenced by various factors, and it's essential to prioritize your well-being and emotional health in any situation.