Q: Oil steam exhaust pipe

Sometimes when I start my car it blows oil out of the exhaust pipe. Not all of the time though. And sometimes it’s steam, and I'm losing water, too. I have to put water in the radiator all of the time to keep it full. These 2 problems happen at startup only. It runs like a Pro once the cylinder has burned out the oil or water. I thought the only way for water to get into a cylinder is a blown head gasket or cracked block. And that the only way oil can get in is through the rings or valves seats. I started my car yesterday, and I didn't have any burn off. Then I drove 5 miles to the post office. When I started it up 15 minutes later it overflowed the post office parking lot with steam. Do you know what’s wrong with my car and how I can fix it? Thanks.