Wilfred Laurier

It is quite likely that your bike will not fit tires wider than 25 or 28mm. This is true of many road bikes. I made the wide tire suggestion not knowing what type of bike you have.

As for performance drop with wider tires, actually no. That was what we used to think, but the current prevailing theory on tire performance states otherwise. Wider tires will lose a bit of energy to increased aerodynamic resistance, esp. at higher speeds, and the weight of wider tires is usually a bit more, so a little more to carry up climbs. But if you get a set of wider tires with a more supple casing (as compare to super-rigid flat resistant tires) then you will generally roll slightly easier on flat ground. In the end, because of the weight and aerodynamic trade-offs, there isn't a big difference in effort, but wider tires will give you more suspension and traction, so many non-competitive riders are going wider these days.

Now on to your current setup-
Here is an article I found with a chart with recommendations for pressures at different tire widths and wheel loads. You wheels will be a the far right side of the chart (wheel load would be around ~55-60% of your total weight on the rear and 40-45% on the front). This would put the pressure recommended (by this chart) to be around 130 - 150psi. That will likely be less comfortable than what you have now, but probably roll much faster and prevent flats better.

Take this all with a grain of salt. If what you have now is working for you then that's great, but I can't help but think your tires are underinflated for your weight.