Hi , Please Am Really Worried , I Had Sex

Hi , please am really worried , I had sex with hiv positive partner ending of last month and I experinece condom burst during intercurse though I removed my penis immidiately like 3 to 5 seconds, and she is on antiritroviral drugs for atleast 4months now. I later rushed down to hospital after 25days to get myself tested and it was negetive. But am still worried. Please what are my chances of not contacting hiv.