Uy, kaya mo yan mama! Low-lying placenta is actually quite common at 4 months, at marami sa amin natakot din like you, pero ang good news is marami ring bumaba pa ng placenta as the pregnancy progresses, kaya don't lose hope! One of my mum friends had the same thing and by 7 months, it moved up na, so just follow your OB's advice strictly (no sex, heavy lifting, strenuous activity) at mag-rest ka talaga, and most importantly, balik ka sa OB for follow-up ultrasounds para makita kung gumagalaw pa ang placenta.
Hindi kami naglakbay ng malayo when we had similar concerns, medyo nag-focus lang sa home rest at pampering ourselves, pero siguro okay lang yan kung malapit lang at very careful ka sa movements, mas safe talaga na tanungin mo directly sa OB mo kung pwede ka pang mag-travel, kasi depends sa severity pa rin at how your pregnancy's progressing.
Tsaka mama, kahit walang spotting now, important na i-report mo agad ang any signs of bleeding o cramping, okay? You've got this, and the fact na you're already taking precautions shows you're doing great. Sending you strength, and fingers crossed na bababa na yan ng placenta!