Just because because FHA regulations stipulate a minimum of 620 does not mean loans are actually being done these days with those sorts of scores. 620 or below is rated as poor credit. Anyone with "poor" or "fair" credit scores is a subprime mortgage, and there are no more subprime mortgages.
These days you need credit score of at least 680-700, track record of at least 3 years on the job, with 20% cash down plus all closing costs plus 3-6 months of reserves. No collections accounts or past due accounts. No new car loan within the past year. Anything less than all this means a high probability of lender declining the loan, or "last minute glitches" with "approved" loan going unfunded at closing. We're still seeing inordinately high rates of unfunded mortgages - something which NEVER used to happen. And all those unfunded or rejected had scores below 700, and/or less than 20% down.
Your credit is not good enough for today's market conditions. This is not 2006! The market is still declining, with new home construction declining again, foreclosures rising sharply, and home prices still dropping in most markets.
Even if you could get a mortgage now, it would be an incredibly stupid thing to do when your credit stinks, and house prices are falling. You'll probably be underwater in your mortgage within 6 -12 months if you put down less than 20%. You'll probably be underwater in your mortgage within 6-12 months if you get an adjustable rate mortgage (ARM). You want to lose your house this year or next?