Is this a business? Is it a Single Member LLC that has NOT made an election to be taxed as a corporation?
If so, from an income tax viewpoint, the LLC is "disregarded", so it has no meaning. For income tax purposes, it doesn't matter if you paid it from your account or the LLC account. In other words, you can still deduct the expenses.
If that is not your situation, the answer may be different.
The purpose of an LLC is legal protection. Mixing business and personal by paying business expenses with your personal account could eliminate that legal program, which could defeat the purpose of having an LLC. If you are concerned about legal protection (which seems to be the case if you formed an LLC), you should discuss it with a business lawyer.