My partner got a vasectomy in january this year, they cut, cauterized and suture ligated the vas. it was successful cause he tested in may and the sperm count was zero. can i still accidentally get pregnant? can the vas recanalize after a few months?

In medicine we are taught to never say never. However, this is one situation where this may not apply. You require sperm to get pregnant. If there is none, no pregnancy will result. If the vas regrows and re-attaches ( extremely rare but theoretically possible) it might.

What you described is about as fool proof as it gets. You cannot pregnant from sex with the partner you described. Practice safe sex : https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines Get HPV vaccine.