We use Salesforce (combined with ecquire.com) at Mixpanel - it's not a very friendly UI but it has every feature you'll need in the future. You learn to love it. Plus, every sales person you may hire in the future will already know how to use it (or should). Salesforce, like most CRM tools, has a way to bcc your emails to keep track of the conversations you're having.

You need to start hiring another sales rep too if you're handling 100s of leads by yourself.

You should begin building a qualification framework to understand which leads are valuable and worth your time: Do they have budget? Who has the authority to get this deal done? Do they have a serious need? When will they buy if everything about your product was perfect? And any other unique factors related to your business. Then, get this information into Salesforce!

It's probably time to start using marketing automation/drip campaigns to keep your leads warm too.

Depending on how long your phone calls/meetings run - you'll usually only be able to handle 5-6/day assuming you're doing this full-time so you should consider calculating how many things you can juggle at once.

Use CRM to build a forecast so you can measure your effectiveness. A forecast is as simple as taking the amount of money you might make from each customer that month and multiplying it by the probability you'll close that customer. That'll force you to prioritize.