Autofac Nhibernate memory leak - memory-leaks

Question

We have WCF Services using autofac and FluentNhibernate. The issue is that it is resulting in memory leak. After every 2-3 hours our application becomes very slow and we have to restart our app-pool.
The following is the code in our Application_start for Autofac registration of componenets in our Global.asax file
What can I do to solve this? Or where start to look for?
var builder = new ContainerBuilder();
builder.RegisterAssemblyTypes(typeof(IPwoSummaryCategoryService).Assembly).AsImplementedInterfaces();
builder.RegisterType<TemplateServiceCollection>().As<ITemplateServiceCollection>();
// Register Singletons
builder.RegisterType<QueryFacade>().As<IQueryFacade>().SingleInstance();
builder.RegisterType<CommandAggregator>().As<ICommandAggregator>().SingleInstance();
// Register open generics builder.RegisterAssemblyTypes(typeof(ICommandHandler<>).Assembly).AsClosedTypesOf(typeof(ICommandHandler<>));
builder.RegisterInstance<MessageBrokerClient>(new MessageBrokerClient(Activator.CreateInstance<CustomMessageFormatter>(), AppConfiguration.MSMQRequestQueueUri, AppConfiguration.MSMQUser, false))
.As<IMessageBrokerClient>().SingleInstance();
builder.RegisterInstance<Logger>(new Logger(HostingEnvironment.ApplicationPhysicalPath)).As<ILogger>();
builder.RegisterType<QuotesUnlockedByAdmin>().As<IQuotesUnlockedByAdmin>().SingleInstance();
// Register the Seed Data Builder
builder.RegisterType<SeedDataBuilder>();
// Register WCF Web Services
builder.RegisterType<QueryService>();
builder.RegisterType<CommandService>();
builder.RegisterType<MasterDataService>();
builder.RegisterType<AuthenticationService>();
builder.RegisterType<UserProfileService>();
//builder.RegisterType<OfflineSyncService>();
builder.RegisterType<ExternalDataQueryService>();
builder.RegisterType<DataContextProvider>().As<IDataContextProvider>().SingleInstance();
builder.RegisterAssemblyTypes(typeof(IDataContext).Assembly,typeof(DataContext).Assembly).AsImplementedInterfaces();
// Create a single Session Activator (manages multiple Session Factories) per AppDomain
builder.Register(context => SessionActivator.Build.FromConfiguration(new Configuration())).As<ISessionActivator>().SingleInstance();
builder.RegisterType<DataContextProxy>();
// Custom Registration for the CurrencyConverter
builder.Register(context => new CurrencyConverter(context.Resolve<IMasterQueryFacade>().GetCurrencies())).As<ICurrencyConverter>().SingleInstance();
var container = builder.Build();
AutofacHostFactory.Container = container;
ServiceLocator.SetLocatorProvider(() => new AutofacContrib.CommonServiceLocator.AutofacServiceLocator(container));
// Pre-populate the database with seed data (if missing)
container.Resolve<SeedDataBuilder>().InitializeSeedData();