halfguard nightmare

basically was wondering if anyone could give me some tips for my half guard. rolled with a guy last night who is propably 15 kg heavier than me. the problem always seems to be getting my head, hip and body the same side as the lockdown as the opponent usually wants ur head on the otherside so u dont shrimp out and take his back on the lockdown side. tried the jaws of life but like i said they guy was strong and had good pressure. i ended up letting the lockdown go and getting a knee shield and an overhook to make space and then went to full guard. just a few questions does the whip up usually work with bigger opponents, is it advisable to maybe quickly switch to the oppents other leg with the lockdown if the opponent has pressure and will not let ur head and hip over to the side u want and finally is it just my defence and should i work on getting on my hip straight away and focus on pushing off his shoulder to make space fpr sweeps etc. would appreciate the help as it is constantly happening :)