I am too worried about my girlfriend last period date of my gf was 21 july on 3 aug we had sex before penetration i ejaculated my sperm outside because of masturbate and cleaned my properly with a clothe after that i inserted my only 2 time not ejaculated

Wait: Not much you can do but wait. If it was sooner then she could have considered emergency contraception. Have her see a doctor if she is concerned or misses period.

The basics: Any erect /excited penis is secreting sperm continuously before/during/after ejaculation. It only takes one sperm to get her pregnant. Any time you have intercourse without a properly fitting condom you can trigger pregnancy. If she's not now, never do this again without protection.