You must be evicted in accordance with Virginia's statues. Landlords cannot 'lock-out' a tenant if they do, they open themselves to liability in suit.
Call police if LL attempts to change the locks. If she actually changes them while you are out or unaware, you may be physically barred from entry for a few days, until you can get a lawyer or the authorities to take steps to inform your LL that she is violating state law.
A month-to-month situation allows that either the LL or the Tenant may terminate the relationships--but that requires 30 days’ notice. Failure to pay rent is grounds for eviction, and an efficient LL will begin the process the day after a payment is missed--you already received the Pay or Quit notice. If you fail to pay or quit, LL must then file an unlawful detainer (an eviction suit) in the local general district court. That process can take 4-8 weeks before the court issues a judgment.
Recommend you pay the LL ASAP and smooth over your late payment issues prepared to find another lease agreement because if LL wants you out, you will be gone eventually.
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NO. The landlord must follow VA law related to evicition of tenants. After the 5 day pay or quit notice has been sent, in order to retake the premises he must file an unlawful detainer. I agree with the lawyer who answered above; you should pay your rent as soon as possible and try to work something out with the LL.