My baby is 3 months can she get her 4month dtap early since I'm worried about pertussis or have 2 wait 4 more wks?

See belwo. The dtap cam be received no sooner than 6 weeks after the previous one.
Be patient-avoid rsk. That 1st dose at 2 months has giving your baby a good start. Testing over many years show 2 mo between doses as safe & effective in reducing outbreaks & building immunity.6 wks between doses is the minimum & used mostly for catch up. U can reduce risk by shopping at off hours if baby goes with you, avoid crowds&those who won't vaccinate their kids. Also have adults in babies life get booster.