When I first started out I had only my personal bank account. There were no laws, at that time, requiring anything different. (I don't think there are any laws now, but it's your duty to check.)
However, after a few years the IRS decided to audit my business. Since I had only one bank account, and I got married that year with lots of gifts, it took an IRS auditor one full week, in my home office, to determine I had no unreported income. You do not want an IRS auditor to spend a week on your accounts!
Get a separate bank accounts right away. There is no reason to not do this, and plenty of reasons to do it.
Get a separate bank account. It wont cost you anything and it will radically simplify accounting and make dealing with the IRS easier.
I'll add that making your sole proprietorship into an LLC and setting up the account for the LLC. The reason you want to do this is to protect your personal assets from things that go wrong with your business. Setting up an LLC is very simple in most states. In WA state it took me 20 minutes and cost $200 a year.
In Connecticut you would not be required to have a separate bank account. But it minimizes the little pains that co-mingling your funds will cause you month after month.
How will you measure the success of your business? If you just want to do a little something on the side, then why bother, just use one account. But if you want to grow your business, try to follow best practices from the start.