I have read your query and understand that you are tensed about this issue. I wonder if this was the reason for splitting from your girlfriend.
A lot of men go through different phases in connection with ejaculation related issues. Nearly 40% men have had early/premature ejaculation
(PE) at some point or the other in their lifetime.
With the limited information provided, I am not sure if you suffer from PE. It could be as a result of getting overexcited when you are young and exploring your sexuality. I do not want you to worry about this at all at this stage.
If it continues to remain a problem or you are worrying a lot, consider seeing a specialist.
Hope that helps.