Gas and electric prices have been rising for a few years now. On it's own, what you pay per month doesn't always say very much because it's hard to know if you're paying for past underpayment.
It could well be that £55 wasn't enough - companies are well known for quoting a cheap monthly price to get you to switch to them, only to admit later that it wasn't enough to pay for your annual consumption.
The average for the UK is around £100 pm, so your could be right, but as well as what tariff you’re on, there are several other factors that affect how much you need to pay, such as how often you have the heating on, the efficiency of your appliances, your insulation, what sort of windows you have, whether your energy intensive things like shower, heating, cooker etc are electric or gas, and where you are in the country, as the price of electric varies by area.
The only thing you can do is take energy efficiency measures if you can, think about turning things down/off and always make sure you are on the cheapest tariff for you, by regularly comparing and switching - watch out for contract termination charges though. It's probably generally cheaper to take out a fix, and then look to switch again at the end of the fix and always look for a cashback deal, which you can usually get via comparison sites, quidco, moneysavingexpert or some banks.