Early labor signs?

Hi, I seriously need help. First time mom here and currently I am at my 35th week, ask ko lang if labor signs na ba yung biglang sasakit ang puson at lower back tapos after several minutes mawawala rin naman. Ganyan kasi nai-experiece ko ngayon. And minsan naman sumasakit yung right part ng tyan ko kung nasaan nakaposition si baby. Plus, kinakapos din ako ng hininga minsan. Is it normal or should I be alarmed? And may I know from those working moms like me kung ilang weeks kayo nag start sa maternity leave nyo?