My rear facing convertible car seat doesnt seem secure?

This site can help you locate a place in your area that will make sure that its installed correctly plus its free.

http://www.nhtsa.gov/cps/cpsfitting/index.cfm

Yeah- I agree with the other person who said that that 3 in 1 seats don't fit good. They are just put their to get the parents attention. 3 in 1 seats tend to not fit well at all because they have to fit a newborn and fit a school aged child. I would get a brand new seat. I would NEVER forward face my child if they could fit rearfacing. It is 5 times safer to be rearfacing up to age 2! If you forward face before age 2, you are talking about broken necks for your child. Your child may not die from their broken neck- just paralyzed from the neck down for the rest of his life. In fact, the NHSTA recommends rearfacing up to age 4!

I would recommend the following convertible car seats:

Safety First Complete Air 65 (40 lbs rearfacing; 17 inch top slot)

Safety First TrueFit Series (35 lbs rearfacing; 18 inch top slot about a 26 inch shell)

Diono Radian RXT or R120 (45 lbs rearfacing; 17.5 inch top slot)

Britax Convertibles such as the Marathon 70, Boulevard 70, and Advocate 70- 40 lbs rearfacing, 16.75 inch top slot.

I listed the top slots because most people want to use their convertible seats front facing at some point. When forward facing, the straps should be at or slighly ABOVE the shoulders- when rearfacing the straps should be at or slighly below the shoulders, so harness height rearfacing, as long as below the shoulders, doesn't truly matter. Despite having a low maximum weight limit, the Safety First TrueFit series have tall shells, which means that tall torso children could use it if they weight less than 35 lbs.

I totally recommend the Radian RXT or R120. It is an extremely narrow car seat. It tends to be very big front to back though. This can be fixed if your son has head control, then any convertible car seat can be installed for upright- as upright as 30 degrees. The Radians have a new angle adjuster that is sold separately for about $10. Also, even if he was a newborn, you could install the seat in the center seating position to fit the Radian inbetween the two seats in front. The only downside is that LATCH cannot be used in the center seating position unless the vehicle owner's manual specifically said it could be used. Also, LATCH shouldn't be used if your child is past 40 lbs unless your vehicle AND car seat manuals has said that this is alright to do so.

The LATCH anchors on the outboard positions have a bar across them and in the center the bar most likely isn't there. If your manual says nothing about LATCH in the center, then you will have to assume that you cannot use it.

Edit: If you were to grab the top of the car seat where the child's head goes and push it toward the back that is natural movement in a rearfacing car seat. This is called rebound and is safe. You are only suppose to check for movement at the belt path and move it left to right. Some seats have anti-rebound bar to prevent this movement and others have rearfacing tethers. Only the Radians and the Britax Convertibles allow tethering. Rearfacing is so much safer anyways and I wouldn't worry about rebound.

What car seat? car? Have you tried installing using the seat belt instead of latch?

EDIT the Safety 1st seats Alpha Omega? This are horrid seats to try to fit, worse they are not good booster seats. Does your seat allow for the top slot to be used? the top slot should be at 17 inches for longest use. Just don't expect this to be the 'only eat your child will need'.

http://www.epinions.com/review/Cosco_Alpha_Omega_E...

and how did the fit go with the seat belt? Sometimes you can used a tightly rolled towel to get a better fit. and there should be a car sat tech in your area to help, (fire station, WIC office, health dept, or hospitals might have one)

I would go to a safe seat check or call your local fire department and see if they will check. They should be able to help you get it in securely, and if it's something wrong with it they'll be able to tell you that as well.