how do i get stronger on this workout?

Your form may be off. Keep wrists straight, and as you bring the bar down to your chest, the natural thing to do is let it touch. DON'T! Don't let your arms go past 90 degrees. When you hit 90, push the bar back up. The strength comes as you let the weight down, not when you push it back up, so focus on resisting gravity rather than forcing it up quickly. Also, you need to be doing other chest exercises as well as arms to gain strength. If all you do is bench press, your body gets accustomed to it and you plateua. Take a week or two off from bench press and do chest press instead - lay on bench with two dumbells and press as you would in a bench press, except alter your hand placement by about 45 degrees. Flys will help broaden your chest.

Another thing to keep in mind is how many sets and reps you're doing. If you're going for strength, do 6-8 reps for 3 sets. Take a good rest (minute or so) between sets and get lots of water. If you can hit 3 sets of 8, time to up the weight. I like to start with a weight and if I hit 8 on the first set, up the weight by 5-10 lbs. If I hit 8 second set, up weight again. The last three reps on the third set need to be tough, otherwise you're not doing much good for yourself. (If you're nervous with the weight, get a spotter, don't try to be a showoff. Anybody at the gym will gladly spot you if you work out alone)

Also, don't think that working your chest every workout will make you stronger faster. I work chest once a week. True that the chest gets a small workout on other days, but there's only a focus once a week. Plenty of time for the muscles fibers you tore up to repair, larger and stronger before. If they can't repair, they can't grow.

NO-Xtreme can help you power through some tough workouts if you're into supplements. Its a big red bottle at Nutrition stores or at the gym (albeit much more expensive there).

Hope this helps.

I work out Chest on Mondays and Thursdays, giving plenty of time for my muscles to heal and grow in the meantime. Fill the rest of your week with a mixture of Arms, Back, Legs, and Shoulders.

Oh yeah, and if you want a strong core, do Abs everyday.

Over-train. You are working too hard, and probably are not giving your muscles any time to rest. Work hard, but rest so your muscles can get bigger.