I think it's totally fine - just depends on what he's saying.

He's not comparing you to her, is he? Tell him how that makes you feel. Try to remain calm.

In fact, it is OK to tell him that it makes you feel bad. Don't use the word "jealous" because that does have negative connotations. Just explain that it's no different than talking about one of his living/available exes. That "x-factor" often makes someone feel inadequate or second best.

Most of us have (or will) had many relationships and it's never tactful for your partner to go on and on and on about exes.

Try to ASK instead of ACCUSE. He may not realize he's doing it. Or he may think you're ok with it. But encourage him to seek counseling and remind him that YOU are his partner and not his therapist and that it's affecting you.

Good luck.