i want to add some things as well. although my forehand was quite good even from the very first session i hit, it has come a long way baby. i went through very difficult times. i overhit at first, and then for 2 years i became a timid underhitter. so i'll give you some advice to
avoid what i went through and then an alternative view, in retrospect.
-if your balls are hitting the back fence i am almost certain you are using an oversized, light racquet. throw it away, don't listen to what other people say, ie. "oversized light racquets are good for beginners". they're not. you wont improve if you continue with them. get midplus size. i don't care if you're 65 or 13. 100 sq in maximum to 95 minimum (which i consider midsize, anyway). 100 or 98 sq in. is your safest bet. as for weight, well pretty early on i switched to a 348 gram racquet. i did have difficulty only when i wasn't playing regularly and frequently; when i was in bad shape, both technically and physically. so i know you'll have difficulty in the beginning. in very little time my new racquet did wonders for my game; i was improving even DURING a hitting session. imagine how much difference it can make in the longer run. such a racquet will force you to improve, whether you want to or not
; this is simply because it is more demanding. i'm not saying get a 345-8 gram racquet. avoid anything under 300 grams. avoid anything over 345 as well, at least for now. demo a few racuets within the 310-330 gram range. get one that you think you'll be comfortable with. if you think you can handle more weight, go for it. there's a lot more that can be said regarding racquets but i'll end it here.
-avoid semi-western and certainly western. my opinion maybe, but they're worthless. unless you're trying to go pro, it is sensless to use those grips when starting out. they're very demanding, preparation/mechanics are more complicated; and they're not versatile. at a non-pro and non-academy level, the amount of errors and lack of control/consistency will be huge. i see it almost every single time i watch a youngster play. believe me even our local club teacher, who thinks he's a hotshot, is making a ridiculous amount of mis**ts or weak shots because of this modern extreme topspin obsession. imagine how much you'll suck trying to hit like nadal and co. Avoid any extreme grip and stroke style in the beginning. go simple, basic. tweak as you improve and gain consistency. only after you've reached a certain level you can start to modify your grip and strokes according to your natural strengths and weaknesses. and of course depending on your raw talent and tactical intelligence. i use an eastern grip mostly. it's suits my game well. with it i can hit heavy topspin (but not extreme) deep if i want to, but i rarely need to because of my style of play. which brings us to my next point:
-to avoid hitting long AND still hit a very powerful shot, i take the ball as low as i can. my swing is more vertical than horizontal - relatively of course. i brush really hard and still swing a bit forward as well as slightly shifting my weight toward the front (along with a body uncoil). this creates a moderate amount of topspin while still making the shot look flat. for my shot, the spin/height effect peaks way before the ball clears the net. therefore the ball clears the net by just a few inches and then goes parallel and downwards. the shot is very strong and deep. this is of course for my best shot. when i really go for it. but basically my forehand stroke is roughly built around this. try this. i think it can help. i seldom hit out now. and certainly hardly ever more than a foot, at least after i'm warmed up and have found rhythm. so as you'll surmise, practice, practice, practice. and since you've been only playing for a few weeks now, i'll give you another tip that contradicts what i've said before:
-DON'T HIT HARD! just try to keep it in and as deep as you can. work on control, stroke mechanics, accuracy and consistency rather than looking at the shot you've just hit and giving yourself a grade. results will come with time. i became a very timid, bland hitter, especially during matches because i feared hitting out. guess what, i ended up putting many balls into the net and the rest into the opponents comfort zones. i considered myself a wimp, one who'd never be able hit winners (without sacrificing percentage) or be able to play a good baseline game. but now i'm glad that i chose to underhit rather than overhit because it allowed me develop control, placement and consistency. power should be the last thing you want to add to your game improvement. your reward will come late but it will be very big. well i hope for you anyway.