Ate, totally natural yan! A lot of us go through the same guilt dahil love namin parents namin pero kailangan na rin namin ng sariling space lalo na may baby ka na, ang dami ng pressure pag maraming tao sa isang bahay, lalo na pag hindi lahat nagkakaintindi. Honestly, one of my mum friends was in exactly your situation, at what helped her was talking to her parents little by little (not all at once) about the plan, making them feel it's not about leaving them pero about being a better mom to her baby kasi stressed ka talaga sa setup. Start simple lang, "Ma, Pa, plano namin next year na mag-start ng sarili namin kasi gusto naming mag-adjust well para sa baby", at involve them in the "why," not the "when" muna, para di agad defensive sila.
For what to buy pag bumukod, honestly prioritize basics na functional, matress, pot and pans, plates, sarili ninyong bedding, curtains na, yung medyo ma-appreciate ng baby for comfort, hindi iba. Then bili bili lang ng furniture pag stable na kayo financially; hindi urgent lahat. And hey, may maliliit na inuman at bahay items na mura lang ang bili pero tumatagal, check hardware stores or SM Home.