I got married on the 6th march 2021 and i was a virgin but my erection is weak. when i got to the second round i shut down before ejaculation and this frustrates my wife?

Analysis of data on young men presenting to a urologist with ED, ages 14 to 27 years, found that 74% of these men coming to major medical centers had a physical problem, and 60% of those had an underlying vascular problem. The rest had a variety of causes including psychological. You should see your Dr for a thorough exam and potentially a referral to a urologist. Early treatment is vital.

Do not understand your 'second round'. Most of the time in young people who had normal erections before, performance anxiety plays a major role during initial sex. I am sure you can work this out with an understanding and cooperative partner. Relax and try this. If it does not work see a sex therapist. If you had problem with erections before marriage see a Urologist