Since it keeps coming back on and off for 2 months, I would just bring your baby to the PD or polyclinic the next time it flares up, even if it seems minor, because at 4 months old it is really better to get a proper look from a doctor than to guess. My girl had something similar and I kept delaying too, but the PD was actually really helpful and I wished I had gone sooner instead of worrying for so long.