It is possible that the main reason you find the Glock hard to conceal in certain clothing has to do with shape more than size (it is pretty "blocky"). In that case, I'd suggest various double stack compact autos. CZ makes several nice choices (RAMI and PCR) as does SIG (I loved my 229). However, it sounds like the main problem may be in the thickness of the gun. Your PF9 is single stack, the HK P7 you are considering is nearly a full-sized service pistol, it is heavy, but it is a single stack.
Single stacks are noticeably thinner which can make a big difference in the concealability and comfort of a CCW pistol. With some carry types (IWB) it can be a bigger deal than other aspects of size (a longer gun, so long as it isn't so long as to interfere with sitting, will still disappear IWB). Even weight can largely be overcome by most people with a good belt. How thin or thick it is can't be easily disguised however, and it can have a huge impact on concealment and comfort (it may be the main factor in whether or not there is a visible lump).
Some good single stack guns to consider:
-HK P7. You seem to like it, they have a great reputation and most people who own them seem pretty happy with them. SAO can be a nice plus- great trigger, no DA/SA transition, infinitely nicer trigger pull than a DAO. They are a bit on the heavy side however.
-1911. Nice thin design that is very easy to hide IWB. Get a 4" Commander sized model and it hides even better (IWB or OWB). Go with a lightweight (scandium from S&W, aluminum from most others) and it will be reasonably light as well (27-28oz for a 4", 32ish oz for a full-size). They are usually .45ACP which is a very nice defensive handgun caliber. 1911 triggers, the standard everyone else seems to strive for- smooth SAO, no DA/SA transition, even my cheap Charles Daly beats all my DA/SA guns SA pull (and the Glock pull by a mile) and my S&W 1911SC and my buddy's Kimber are quite smooth (nothing like a good 1911 trigger pull).
-Walther PPS. I have no firsthand experience, but most owners seem pretty happy. A PPS in .40 is high on my list for my next couple purchases as well. VERY narrow, available in decent calibers, apparently reliable, they would make a great single stack CCW.
-Kahr. I've had Kahr on my list for years- first I wanted the K9, then the PM9. I haven't got around to buying one yet, but I will. My best friend had a MK9 which was highly reliable (100%), accurate (esp. for such a small gun), comfortable to shoot, and very well made (great workmanship). The only drawback was it was fairly heavy for the size and caliber (a pocketable 9mm shouldn't be 22oz). He now owns a PM9 which is also a great gun. It has noticeably more recoil, but it is far from uncomfortable (I'd say it feels similar to an all steel J-frame .38spl). It is accurate and reliable. If you want a 9mm I'd wholeheartedly endorse the polymer frames, if you want a .40 I'd probably go with the steel models. If you don't want to ever pocket carry the steel 9mms are just fine too. The only drawback I see is price (the reason I'm still without one), quite a few guns of similar quality seem to run about 10-15% less than the Kahrs.
-J-frame in .38 or .357mag. I know this is the auto section, and you seem to want an auto, but from the sounds of it, a J-frame may serve your needs quite well. They are narrow and easy and comfortable to conceal. The different lumps and humps on a revolver conceal differently than an auto and if a lump happens to show it seems to be less obviously a gun (though they are small enough no lump should show with IWB or OWB carry). They are usually more reliable than an auto- with most autos it is recommended that you put several hundred rounds through it, usually with your carry ammo, before trusting it, while most revolver guys are quite comfortable shooting a box of ammo (or less) to function test it (and you don't have to worry about it when you change ammo since different shaped bullets have no effect on the reliability of the gun unlike with autos). The two drawbacks are that small snubs are among the hardest guns to learn to shoot well (the combo of the sights and the relatively light weight for the calibers tend to make them tough to master) and you only have 5 rounds in a snub (6 with one of the smaller calibers like .32H&R mag or the newer .327mag, or 6 in .38spl in the new Taurus 856 or old Colt snubs, but then you have a slightly larger/wider cylinder).
