As your subscription has now run out, your maximum stored messages allowence has dropped down to 10. Looking at your profile it says you currently have 7 messages still in your sent folder and 1 in your inbox making 8 in total, so you should be alright to send at least 1 message and have space for a reply.
Otherwise try deleting the messages in your sent folder or resubscribing which will give you an allowence of 150 again
Hope that helps.
P.S, don’t worry the system only shows the message statistics, it does not show the message contents or titles.